Graphical Web Browsers

What web browsers should I test DisOrder against? I've successfully tested with:

• Firefox 2
• Konqueror 3
• Safari 3
• MSIE 7
• Opera 9
• Seamonkey
• iCab

Are there any other at least reasonably widely used browsers, ideally that I can download for free, that I can test with?

(See comments re IE6, and browsers I've tried that don't work.)

( Relevant bits of changelog )