There's hundreds to thousands of people who like heartbeats and actively participate in heart-related activities scattered across this big ol internet thing, here's where you can find them.

There's a handful of sites dedicated to hosting cardiophile communities, most of us are on at least one of them.

Heart2Heart
YOU ARE HERE.
The youngest and second-most popular dedicated site. In a lot of ways acts as a central hub to a lot of other split-off segments of the community. It's my personal favorite, and focuses more on providing a calmer area for people to share their interests.

Features: Live public/private streaming, live public chat, forums, secure file sharing, blocking, private messaging, cross-site integration with YouTube, Tumblr, and Discord, and more!

Heartbeat Pleasure
The oldest and most popular dedicated site. Very closed off compared to other sites. An NSFW section exists for people who donate or contribute many files over a long period of time. Adblockers are banned, as are anti-tracking addons that happen to block ads.

Features: Live public streaming, live public chat, forums, secure file sharing, blocking, private messaging, and more!

The Art of a Heartbeat
A ProBoards forum by Tumblr user BellaHeartbeatQueen. Last forum post was in August 2016, but there's a small chunk of stuff to check out if you're interested. Also paired with an active SFW community blog (Posts accepted by outside users) that shares a *lot* of heart-related art.

Features: Tinychat-based live streaming and chat, forums, community-fed blogs, and more!

CardioAuthors
A ProBoards forum by Cardiopium. Heavy focus on creative writing and sharing stories.

Features: Forums, and more!

These dedicated sites offer the most dense concentration of hearty people and content, but there are other huge pockets of cardiophilia on the net, too.

Tumblr
Tumblr's cardiophile community might just be the most active and popular of any site. Lots of content of all kinds, audio, art, video, text posts, stories, you name it. Check out the #cardiophila, #cardiophile, and #heartbeatfetish tags. If you're having a hard time finding people to follow, check out the Tumblr directory below.

Discord
If you like chatrooms, there's quite a few Discord servers dedicated to hearts. Discord supports live streaming and listening, as well as private chats and calls. The chat also supports file uploads, video/audio embedding, and link previews. If you want to know where to go, check out the Discord directory below.

YouTube
There's a fairly active network of uploaders on YouTube. You probably know YouTube. Upload videos, get comments on videos. YouTube also supports easy live streams, and there are a pretty good number of channels that broadcast live often. For a list of channels, check out the YouTube directory below.

Smaller groups
There's a few other tinier groups and such scattered across the internet. Kik groups, Skype groups, that kind of deal.

There's one open Kik group I know of, you can get yourself invited by posting in this thread.

On Amino there's also this cardiophile group.
And this furry cardiophile group.

Best places for streaming are Heart2Heart, Heartbeat Pleasure, Discord, Skype, and YouTube depending on your needs.

Heart2Heart is great when you want to broadcast high-quality heartbeats to a lot of people. It's up to you whether you limit your broadcast to H2H members or let anyone in. You can also hide your stream from the public listing if you want to share privately. Allows but doesn't require specialized streaming software.

Heartbeat Pleasure is great when you want to broadcast high-quality heartbeats to anyone who's a member of HBP. Requires specialized streaming software.

With H2H and HBP, that (optional for H2H) "specialized streaming software" you're looking for is any streaming app that can handle Icecast. On iOS, your only options are iCast ($24) or Heart2Heart's in-site streaming button which works for both H2H and HBP. Other options for streaming include:

Discord works for whoever, but audio is tuned for real time voice chatting, and loses points on quality. Upside, it's available everywhere on every platform, streaming doesn't require any software downloads, and it's pretty easy to use. Can stream live to an entire server, one on one, or a private group.

Skype, in my opinion, is going downhill. But it still works absolutely fine for now. Shines brightest when used in one on one situations.

YouTube works well, good quality, downside is that streams need to technically be videos so either tape over that webcam or just broadcast straight black the whole time. Or don't, that's cool, too. YouTube wasn't made for this, but it works well and offers things nobody else does. Features a live chat (that YOU moderate) and the ability to play back your stream later effortlessly.

There's a lot of options when it comes to making friends and meeting people. The most popular platforms for private chatting are Skype, Discord, and (sometimes) Kik.

Skype is available everywhere, there's a web client so you don't need to install their app on your PC, works reasonably well, works cross-device and cross-platform, and stores chat history.

Discord is also available everywhere, also has a web client, works pretty well. Works cross-platform and -device, and stores chat history in a very searchable form. Because if its focus on group chatrooms, it's a bit easier to find people to PM without asking around on other sites.

Kik is only available on phones. Both iOS and Android, and only one device at a time. Chat history is stored, but if you move devices it's all lost. It's still a very popular option for texting and swapping photos (no voice or video calling), and has read/unread markers for messages you send.

Lotsa Discord servers out there. When any of these servers become active, they show up on the front page of Heart2Heart.

Anthro Hearts
An active server with more of a focus on RPing and furry stuff and furry drawings and all that jazz. Both SFW and NSFW

Cardiophiles of Aperona
A more general server many, many different channels for all kinds of different interests. There are rooms for discussion and art both SFW and NSFW.

Cardiophiles Anonymous (NOW DEAD)
A pretty active server more narrow in scope than Aperona. People stream and upload files here pretty often. Has rooms for SFW and adult conversation and recently an NSFW channel as well.

There are also other active servers out there that aren't listed on H2H's front page.

Cardiophiles!
A cardiophile server with both SFW and NSFW sections.

cardiophile fr/vo
A hybrid french/english cardiophile server run by Tao Ott.

Heartbeats and Everything Else
A newly-formed server with an emphasis on free speech.

Mongrel's Lair
A strictly 18+ only server with heart content of all kinds.

There's a good number of heartbeat channels, you can find more through the "Related videos" and "Related channels" features, but here are all the blogs that have all their latest stuff slipped into Heart2Heart's activity stream.

Simoh Heartbeat
A cardiophile dude with a lot of content. Heartbeat audio with videos of himself recording.

thewyrdguy
Cardiophile channel with a lot of audio uploaded. Occasional videos, too, even a few visible heartbeat ones.

Gillian T
Cardiophile woman who streams a lot and uploads a lot of restful/ASMR audio.

Heartbeat Adventures
A channel with a lot of detailed audio files. She does live streams occasionally and has a few visible heartbeat videos.

Mind-bending number of blogs out there, and I'm pretty sure Tumblr has more cardio content than any other place on the internet, if you know who's posting it and how to find them.

Blogs with a star* have agreed to be slipped into the activity stream on the front page of Heart2Heart.

• Chirabeats*, My blog. I mostly reblog hearty images from wherever I can find it and post helpful things whenever I can. SFW

• KGV41*, "A 19 year old British girl who likes hearts a little too much", she posts a lot of original heart audio and hosts YouTube live streams pretty often. SFW

• Heartskip-of-Rose, A cardiophile artist who posts a lot of original artwork and reblogs a lot of audio/visual files and cute text posts. SFW

• She's Everything to Everyone, LOTS of high quality cardio stories. She doesn't write anymore but she has a very large library stored in her blog. SFW

• hbplvrsblog, Cardiophile dude who is up for DMs. Lots of discussion posts and reblogs of art/images. SFW

• heart-angel*, Mildly active cardio blog with lots of audio posts, original photos, and text posts. SFW

• heartbeatadventures, Cardiophile woman who live who does *lots* of live streams and other videos on YouTube. Uploads a few photos and other things as well. SFW

• cardiaccadillac, A cardiophilia/supernatural crossover blog. Curates a lot of art and photos. Lots of stories to read here, too. Lots of creative content in general. "Occasionally NSFW"

• pastelpink-heart, Cardiophile lady that posts lots and lots of audio files. Also occasionally reblogs cardio-related images and photos. NSFW.

• stethingdave, Cardiophile dude who posts. A *lot*. Of everything. Stories, original photos, cardio and fluffy content of all kinds. Lots of neat SFW stuff, but NSFW

• eulalia-heart, She reblogs a lot of heart stuff from a lot of places, good general cardio blog. NSFW

• cassandra-heartqueen, "A mother with an enlarged heart", posts a lot of content both hearty and not. Also posts her own drawings and OCs. *Mostly* SFW

• darkchestofmyeye, Lots of heart porn, mostly hentai flavored. NSFW

• resus-girl, The very active blog of a cardiophile woman with a big emphasis on resuscitation. Videos, photos, stories, discussion posts, everything. Lots of NSFW.

• iwannafeelyourheartbeat, A rare cardioblog with stuff for dude-attracted individuals. Basically SFW? Lots of bare chests ofc.

• hummingbirdhearts*, A couple-run cardiophilia blog with lots of artwork, text posts, stories, and other fluffy cardio stuffs. SFW

• check2345, A pretty cool dude who does a lot of video edits. Not super active but good quality blog. NSFW

• heartbro95, Cardiophile writer with a lot of text posts and audio files. "This blog contains mostly writing, heart sounds, and writing about heart sounds." SFW

• the-heart-is-beautiful, Lots of photos, erotic cardio stories, and medical/resus content. NSFW

• captredheart, Mostly hentai and furry heart porn. Not super active, but a very large archive. NSFW

• krissyfoxx*, Cardiophile gal with a lot of text and light image posts, with some interesting discussion and info posts. SFW

This list is very much incomplete, and I plan on expanding it whenever I can.