I f you're not using Firefox browser yet you're not going to understand why I'm giddy about something called extensions. Since Firefox is an open source software anyone smart enough to write a way to extend it's functionality can make my browsing experience better. Now, like a lot of things that can be done, you have to wade through what should be done and used to make your browsing experience better.
Here are my top 5 browser extensions in no particular order
del.icio.us bookmark - lets me copy some text on any page and post it to my delicious account
SEO for Firefox - Aaron Wall's treasure chest of info on search results
Fleck - This one allows you to make notes and lists on web pages and then send the annotated page
Search Status - simply tool that sits in my dock on the browser and gives me page rank, alexa ranking, backward links and indexed pages for any site on visit on the fly
Roboform - fills in forms and keeps track of passwords and the like
And a bonus one that's kind of funny - BugMeNot - allows you to skip putting your info in to get an article on sites like the New York Times