20 must-have Firefox extensions

mrbluze writes: "Computerworld has an article: http://www.computerworld.com/action/article.do?com mand=viewArticleBasic&taxonomyName=development&art icleId=9011975&taxonomyId=11&intsrc=kc_feat which reviews 20 useful Firefox extensions. I must admit this was a very fruitful read and identified some extensions that don't usually come up when you browse the 'popular' list on the website.

Do fellow slashdotters have other extensions they cannot live without?"