I've been updating Firefox add-ons that I had to disband during the beta. Of course I'd never remember all the add-ons and Greasemonkey scripts I liked, so a while ago I made a general guide for just this kind of situation. I was pleasantly surprised to see how many things have become unnecessary as Fx has improved: AutoLogin script, change email links to a webmail client, Google suggest, and hiding gmail spam numbers (actually a Gmail improvement), and a Growl-Firefox application. Foxmarks should be replaced by Mozilla Weave eventually and the Activities add-on as the Web evolves to catch up with Firefox's microformats.
I also noticed how many Mac OS X applications I don't need anymore because OS X has created better replacements in the latest version: Chicken of the VNC (for screen sharing), Boot Camp, Monolingual (decreases OS X's footprint), X11 (a Unix framework), Uno (changes window appearances), and a virtual desktop app. The next Quicktime honestly looks like it may decrease my reliance on all the media codecs I have, support for more compression formats, and exposure to their hibernation support which Apple hides for some reason.