I’m not on Windows but I think Firefox extensions work on Mac as well, so here are some of my favorite add-ons: Adblock All-in-One Sidebar Compact Menu 2 CustomizeGoogle Download Statusbar DownThemAll! dragdropupload (drag and drop from open folder to “browse…” bars in websites) ErrorZilla Plus Fast Dial Faviconize Tab feedly (organize feeds in a newspaper-type layout) Fission Flagfox Foxylicious Google Icon Google Gears Greasemonkey (the scripting engine to modify webpages) LastPass (password manager, encrypted, integrates with all current passes and syncs between computers) Linkification Locationbar^2 (stylized location bar) Menu Editor NoScript Organize Status Bar PDF Download PermaTabs Mod (permanent tabs refitted for Firefox 3) Searchbar Autosizer Stylish (change CSS of webpages, tweak Firefox interface) Tab Mix Plus Taboo translator Ubiquity URL Fixer Also, there is this experimental extension called Tabgroups-Plus that allows you to organize open tabs into folders. However, it is experimental and I’m not going to recommend it unless you want to try it on your own accord. Bolded are the ones I favor the most, and why.