I am sure about firefox web browser being the most used program for many computer users. I spend a lot of time on firefox (basically whenever I am out of coding). So, what I like is to customize it to my taste and necessity. I am sure you know of Firefox Add-ons too.
If you were looking for something, and could not find it through google search, here are two lists of (almost all) useful add-ons.
I want a Firefox Extension to ... 200+ extremely useful firefox extensions that save time and effort.
and
Best Firefox Extensions
I use quite of them, especially Mouse Gestures, ForecastFox, Foxmarks, Dictionary search, PDF Download (very useful), Browster (preview) etc. I used to had a lot of them, but then I started having problems with Firefox. It was slowed down considerably, and I could not even type the search pattern in toolbar. I think (if I remember it correctly), those extensions (or add-ons) were related to tabs. Greasemonkey extension also gave me trouble, but since I don't do any web scripting, I uninstalled it. So, I would say that install them one by one (the ones you really think you need), and see if its affecting your usual browsing experience.
The one extension I didn't see in these links was Google Notebook add-on. You may find it useful too. Also, some extensions are out-dated, like, SpellBound, and these features are now part of browser itself. Few weeks back, I used (much-hyped about) Firefox 3 beta, and it has also incorporated more of the features, which previously extensions used to provide, e.g. enhanced bookmarking, and better Download manager.
Happy browsing, with firefox...
