Over the next couple of months, I'm going to blog about my absolute favorite Firefox extensions. It might be useful for some people ;)
One of my most recent extensions (and already one of the most useful). GreaseMonkey enables you to "load" any given piece of DHTML while loading a page, hence enabling you to change the behavior of the page. Fx. a small script is Linkify (if you have GreaseMonkey installed, you can right click on the link and press "Install User Script"). Linkify well crawl through all the contents of the loading page, and change all URLs that do have an <a href=... tag - so that you can click on them.
There are hundreds of ready-made and ready to run scripts available here: