Erik Deckers said
12 months ago: @mellissathomas I like Posterous, but they were recently bought by Twitter and the buzz is that this was strictly a talent grab, and not a “hey, this is cool technology” grab.
If you read Posterous’ FAQ on the buyout, you can see they keep making poorly-veiled references to their imminent demise. So, I would skip Posterous and go with Tumblr instead.
My personal favorite is a self-hosted WordPress (.org) site because it can do so much more than any other platform. Sort of like owning a race car when all your friends own mopeds. But if you just want something to goof around on, Tumblr is a good one.