We Mac users take our web browsers seriously, which helps account for the fact that there are just so many of them to choose from. For my money the top browser on OS X is Camino (though Safari 3 is closing in fast). Camino, as you can see from the accompanying picture here, makes a big deal out of its 'Mac Style,' and it does feel much more at home on a Mac than Firefox does (though the Firefox team is working on that).
Camino is free, as are most browsers these days (Ominweb, I'm looking at you), but that doesn't mean you can't chip in to support development. The Camino Project recently announced that they can now take donations. Working with the Mozilla Foundation the Camino Project has setup a way for you to donate money to support the app, and get the added bonus of writing it off on your taxes. Best of all, the Mozilla Foundation will offer a 2 for 1 match until the end of the year, or until the donations reach $10,000, whichever comes first.
If you're a big Camino user be sure to head on over to their donation page and send 'em a few dollars.