Web developers, you guys are really lucky. The tools available for you as a group are very powerful and they come in all shapes and sizes. With the introduction of Google Chrome, the community has made some amazing extensions which are very easy to use for every day work. Below you have the ones I consider most useful (starting with the best, of course  ).

http://aext.net/2010/03/extremely-useful-chrome-extensions-for-web-developers/