Marla Swoffer (formerly Proverbial Wife for those who might know her by that but not by her real name) has started TypeBlogs. One of the selling points is a blogroll for each Myers-Briggs personality type, and she's got a link to a quick, online test to discover which type you're most like. [You could also do this short one, this longer one, or this word matching one. Generally speaking, longer tests are more accurate, but shorter ones are quicker to do.
To join one of the blogrolls, see this post.