The first things I do after having “bloody” new operating system set up is to – if not previously installed – install firefox and some extension I need for “daily” tasks.
The first one I think is always PwdHash which generates per-site-passwords on the fly in combination with your master password, so I can login to the bunch of websites where I am registered. Just install it and press F2 when you are in the password box, then enter your password and press Submit. The extension automatically generates the password, so that key loggers have no chance.
Call me paranoid but I use site-specific master passwords too. So like the first and last letters of the website domain with different case combinations and a static part.
After some time of surfing I discover the annoying ads popping out everywhere. The simple solution Adblock Plus which protects me from the time-stealing layer-ads.
After a while I tend to visit del.icio.us to extend my bookmark list. If I see a nice website I want to simply add this page to my bookmarks without going to the del.icio.us page, the click post and the copy the page title to the description field. So I install the del.icio.us Extension (VS 1.2) because version 1.5 works too slow for me. Sure it has more features but I am satisfied with the features of VS 1.2.
The last one I install after some downloads is Download Statusbar which makes downloads a lot easier because it simply shows your downloads in a bar at the bottom, so you always have an overview and can do all important download-related tasks at one place.
In another profile I often install the Web Developer Extension for detecting the structure of a website. This helps a lot when designing a new page. But at the time I have other things to do 😉
You may post your favorite extensions without you cannot live. 😎