In roleplaying, participants adopt and act out the role of characters, or parts, that may have personalities, motivations, and backgrounds different from their own. Roleplaying is like being in an improvisational drama or free-form theatre, in which the participants are the actors who are playing parts, and the audience.I am referring to text based RP. Here you pick a genre, say adventure, drama, horror etc. Or you pick something to base your RP on. A film, a book, a fandom, anything you like. Next you pick a character, your original one, or one that exists already, say, the main character from a popular book.
Roleplaying is not something you can do on your own, therefore, you either join a RP-site or, as I also quite fancy, do it in am IM-program like MSN. The people you play with (one is of course a minimum) also pick their characters, and from there on it's just like story writing, only with multiple authors.
Why is this so fun? Because it creates challenges and a sense of surprise because you never know what the others are going to do or say. It also very often helps me to get rid of a writer's block situation and in the worst cases lets me test whether or not a scene in my stories works. Generally, RP stories never seem to end, which makes them fun and rather addictive.
A blog with multiple authors could also work very well as a RP-platform. One person posts, and the next person replies to that post, replying strictly as their own character. Just another way of story writing really. Hmm, wonder if that would work...