Livejournal used to be really good but they’re dying now. They’ve had to add a lot of ads to stay afloat, and people don’t really go there anymore, which means you’ll get no readers.
I like Blogspot and Wordpress now.
I don’t like Tumblr personally because it seems like writing and reading posts isn’t encouraged so much as posting funny pictures and shit, and that’s not what I blog for. If that’s what you like, though, go for it.