My buddy John sent me documentation of weird CSS bug tonight by using a cool service: BrowserShots.
Drop in a URL,and get 9 screenshots of your site in 9 different browsers. Curious what a page looks like in Safari on Mac? Opera on Ubuntu? Now you can know.
I wouldn't want to test an entire site using this approach, but it's certainly a good idea to try out a few key pages. Definitely a handy utility site to have around.