Since I have a bit of time I'm just going to talk about some of my firefox addons. I personally like to keep the list short (firefox is slow enough as is), especially since I have a lot of bookmarks (which I should tend to over the summer break).
Adblock plus- block ads
Gmail manager- access multiple gmail accounts
Greasemonkey- changes site layouts, pretty useful especially for sites like youtube/facebook
Noscript- block scripts
Tab mix plus- better tab management on firefox
Targeted advertising cookie opt-out (TACO)- apparently it prevents ads from tracking you to make an advertising profile. I don't think there really is a way to check whether it works or not so I just keep it around. Perhaps one day when I'm bored I'll just uninstall it.
So in the end, my firefox addon collection isn't really unique or different, just the usual set that a lot of people use, but when it comes to greasemonkey scripts I guess they're a bit more "specialized" to suit my purposes when viewing sites.
Google calender header and navigation switcher
Google calendar colorize sat/sun
-For the two google calender scripts google might have added calendar options, but I got these scripts a while ago so I keep them around. Last time I checked I don't think they had extra options that performed the actions that these two scripts performed. For navigation switcher it allows me to collapse the header and navigation bars, so it's pretty much a full screen calendar. I personally don't like the navigation or headers because I don't really use them much. If I need to I can switch them back. And for the second script it's just to colorize the weekends, make the calendar easier to see overall.
Facebook ad remover
-Better facebook might be able to remove ads but I wasn't sure. Script basically that remove facebook ads (I don't like all those evony ads popping up on my facebook)
-Adds a lot of functionality to facebook especially on the home page. Allows you to tweak numerous settings. It has a lot of features that you can check out here. It also comes as a firefox/chrome addon but I prefer the script, since I don't need as many addons to keep track of (plus I turned updating off to speed up the browser and this addon has a lot of updates)
Youtube enhancer- I didn't feel a need for this until the new youtube interface revamp, it makes youtube a lot more usable in my opinion, adds autoplay on/off, extra controls (such as repeat a video), can download videos, makes the comments section neater and by default shows the day of the comment (Ex: 5 days ago) where in the current view you would have to hover your mouse over the comment to see when the comment was posted.