I recently posted a question to Hacker News about using Theme Roller for site design. The general concensus was that it’s great, but sometimes looks a little childish. So, a fellow HN user released http://taitems.tumblr.com/post/482577430/introducing-aristo-a-jquery-ui-theme. It’s called Aristo, and it really cleans up the jQuery UI stuff.
Take a look if you get bored. It’s worth it.