Firefox add-ons

There are a couple of Firefox add-ons I find worthwhile having:

Web Development:

• Web Developer - a must have for web designers and developers
• Firebug - ditto, but for javascript developers
• HttpFox - This is useful add-on which allows you to see HTTP protocol information.

Security:

• No Script - prevent web scripts / flash content from running automatically. Can be a lifesaver on flaky OSs like Windows...
• Web of Trust - marks various sites as safe or warns about sites you should avoid

Utility:

• Xmarks - Sync bookmarks across all your Firefox installations (for example on your main computer and laptop, or between house and work)
• ScrapBook - save complete web pages as you see them. This is great for saving pages to which you have limited access (like learning sites which will expire)
• Screengrab - Save viewed page as an image
• AdBlock Plus - skips loading of various web ads and banners.