I recently was pointed towards Ubiquity, which is a cool little firefox 3 plugin that gives you a pop-up query window to have clever web shortcuts.
The video below explains a bit how it works (once you get past the intro).
If you are too busy to watch the video, some of the things they do are translate a chunk of a webpage, email selected text, lookup up a selected address (and multiple addresses) on google maps, etc.
Most of it is centered around google tools (gmail, calendar etc) but many are just useful tools (builtin tiny-url lookup shortcuts, etc).
The best bit about it Uniquity is how quick it is to create plugins for it – I have already written a plugin that lets me do bluepages (IBM’s internal address book) lookups, as well as a plugin that lets me lookup defects and features for a few cmvc (the code/defect tracking tool used in my department in IBM) families
If you are an IBMer and want to try it, see my internal blog for details
Ubiquity is only an alpha release, but frankly it is rather cool already – I can’t wait to see where the next version takes it