Disroot Community

It's more or less similar to Reddit in terms of posting, voting and subscribing. The main power is indeed federation, meaning nobody needs huge servers to keep the network online. As long as instances don't blacklist each other, you can freely view posts from foreign instances, subscribe to communities there and comment, all with an account on your home instance.

There are some gimmicks, like on Reddit you could just write

/r/subreddit

to send someone to a sub, but here you'll have to do

!community@instance

to specify the right place, e.g. [email protected], but it's nothing too crazy.