I prefer roleplaying on Tumblr, so I put it as other since I didn't know what it'd come under haha. I didn't get on well with a group chat roleplay because everyone was sort of fighting over each other to get a word in, but I do IM roleplay with a couple friends. Overall, RPing on Tumblr has been the best experience for me personally, since you can have multiple things going on without worrying about them running into each other or having to fight to get a word in.
Anything, really haha. There's group RP blogs (like the one I was part of which shut down recently =[), and I know there's odd RPers here and there that are willing to RP with anyone. I know there's a lot of Hetalia, Sherlock and Final Fantasy RPing, from what I've seen, but I tend to stick to things that are more original ideas or use OCs because I don't trust myself to be able to keep to an existing character's personality haha.
One of my RPing friends has a habit of wanting to RP her latest favourite movie with me, and she tends to have a habit of using existing characters within that as she sees fit. It annoys the hell out of me haha.
Tumblr does seem to be pretty good for OC roleplays, though, and I use Tumblr anyway so that's a plus xD