Tumblr - Post junk that I think is neat, jot out a longer form thought, and journal my fitness program.
Twitter - See what people are talking about and find out news from links people post
Facebook - play games and see what people are doing
Google + - too soon to tell, but could be combo of all 3…
(By the way, this is mostly for testing the “post to Google+” Chrome extension, so there you go.)