Firefox is a great browser as most of you probably already know. I recently switched to using it as my default browser on OS X because Safari is flakey with GMail. One of the annoying things about Firefox on OS X is you can't tab to drop-downs in a web page. No longer my friends - in this month's Macworld there's a solution!
In Firefox (or Mozilla), type
about:config in the address bar. Then search for "accessiblity.tabfocus". Change the value to "3" in order to allow tabbing to all form elements, or "7" if you want form elements + links.
Now if I could only get my two favorite Safari features in Firefox: auto-fillin of forms and spell-checking as you type.