I saw the 'z4root' application on the Droid market just now. Is it safe to use on my Samsung Galaxy S?
I've rooted my SGS with z4root and it was a very smooth process! I can highly recommend z4root!

And while you're at it, continue with installing One Click Lag Fix to make your SGS lag a lot less! I did it, and haven't looked back since. OCLF is made by the same guy who made z4root, but for some weird reason, OCLF can, by itself, only root pre-froyo phones. But that's not a big problem, you just need 2 apps instead of one :)