If you're as interested in philosophy as I am, then you already follow a few philosophers on Twitter, and you probably subscribe to a few philosophers on Facebook as well. But sometimes you just want to see more.
Philosophy interest list on facebook is a one-click subscription to hundreds of academic philosophers, university philosophy departments, international philosophy conferences, and local philosophy clubs from across all of facebook. Although it sounds like it might be a noisy feed, it is actually a very readable rundown of what philosophers are talking about publicly on facebook in real time. Most clubs, departments, and conferences post very rarely, so even though hundreds of them are included in the list, it never gets overwhelming. Each day, I see discussion on philosophical ideas, a few calls for papers, announcements of talks around the world, and even a bit of philosophy humor from time to time.
The twitter version of this list is, perhaps unsurprisingly, a bit more noisy. Academic Philosophers on Twitter is a list consisting of hundreds of philosophy faculty twitter accounts. A good percentage of tweets are philosophically centered, but I've noticed that, unlike facebook updates, the tweets that philosophers publish on twitter are far more numerous, and tend to be about all kinds of non-philosophical things. It's still an interesting feed to browse, but it's much less significant than the facebook philosophy interest list, at least in my opinion. (For an even noisier experience that includes philosophy students and amateur philosophers, see @ranilillanjum's Philosophers on Twitter and More Philosophers lists. The lists are so full of people that she had to use two lists to keep track of all of them. Nevertheless, they're still worth checking out.)
I should point out that subscribing to any of these will not cause your everyday social media experience to suffer. Subscribing to the somewhat noisy twitter list doesn't clutter up your twitter feed at all; you have to manually click on the list in order to see tweets from it. Subscribing to the facebook interest list also results in very little clutter; although posts will show up in your regular facebook feed, they are clearly delineated and are grouped together so as not to interrupt the flow of updates from your friends and individually subscribed pages.
Every list I've linked to above is one that I personally subscribe to, though the only one I read with any regularity is the facebook one. I hope you'll find these links as useful as I have.
(Incidentally, if you know of a philosopher, philosophy department, or philosophy club on facebook that isn't already on the list, please let me know by sending me a message on facebook. I'll be glad to add them. Note that if you point me to a philosopher's facebook profile, they must allow subscribers in order to get successfully added to the list.)
(Edit: I'd like to append a link to this philosophical humor pinterest account, even though it doesn't really compile professional philosophers' accounts on pinterest in the same way the facebook and twitter lists cited above do. (Added November 2012.))