Tired of refreshing your page to view changes in your CSS? Erik Hanson has a bookmarklet you can use without refreshing your page. See it on his blog.
There is a beta version of the Selenium 1.1.15 gem that includes the latest selenium-server.jar (1.0 beta-2). This fixes some problems with using Firefox 3. You can get the gem here, and you can read the details here.