UTW must be my favorite plugin
Christine has released an upgrade
I also submitted it to Digg, so Give It Some Digging
Honestly I see so many junk plugins on people’s top 10 list that take almost no effort to create (though sometimes serve a useful purpose).
UTW is a little complex, but the SEO benefits of using it are amazing, and often underestimated.
What is especially useful is that this version has already been tested with WordPress 2.1 beta versions. The more plugins you update now with compatible versions, the less pain you will have upgrading to WordPress 2.1 in the near future (maybe less than 1 week away)