Firefox of course.
I didn't know there were any others.......
Firefox 2.0
Opera 9.0
IE7
in that order. I think Opera is a better browser 'out of the box' over Firefox but nothing can touch the 'extensionability' of Firefox.
i'm using internet exploder 7 in work just because i have to, ff doesn't work on our intranet, but i actually like it.Have you ditched IE6?
Does anyone still check if their sites are compatible with IE 5 and 5.5?