So what are your favourite brower add-ons?

Firefox - the king of browers for add-ons

Firefox Add-ons
Explore the many different add-on possibilities on this site. Specific examples are included below.
Colorful Tabs
Colors every tab in a different colour and makes them easy to distinguish when you have a lot of them open.
Download Statusbar
Shows the progress of downloads at the bottom of the browser window. You can also open the downloads from there once they have finished.
Just good fun really though you can often find a gem this way. StumbleUpon discovers web sites based on your interests, learns what you like and brings you more sites it thinks you will like.
Speed Dial
Organizes your favourite book marks visually on your homepage. Click and you get to the most important pages to you. The book marks can also be organized into layers.
The easy way to download and convert Web videos from hundreds of YouTube-like sites. This works also for audio and picture galleries.