Which langauge do you save them in, out of curiousity? I'd be interested in hearing that from others, too. I'm using the ruby driver, personally.
I've been using the ruby selenium driver as well. Works great.
I mostly use the Java unit test format, but I also use the selenium IDE to automate a lot of repetitive setup/config stuff. And I've started using the Lisp API (http://selenium.openqa.org/) for hand written tests.
Watir (Ruby), or for a current project, WatiN (.NET port of Watir).
It's fun to watch.
If you're into Python try Twill, Mechanize and use appropriate tools for Firefox(XPCom--GIYF) and IE (IECom--GIYF).