Dictionary Lookup Extension
While writing my reviews and posts, I always find that I need a dictionary handy and since there isn't one available, I need to type dictionary.reference.com and type in the word and...oh, you get the idea.
The Dictionary Lookup extension provides you with a quick way to find out what a word means without even surfing to another web site.
The extension is activated through the context menu. Highlight the word you want defined and right-click on the word. The "Define..." option should be at the bottom of the context menu. The extension will query dictionary.reference.com and return the definition without even blinking. Well, it may blink a little to load the definition, but it's quick.
If the definition requires a lot of explaining, it provides the entire definition by parsing and adding each line to the context menu. Kind of low level, but it works.
With the newly introduced spell checker in Firefox 2.0, the Dictionary Lookup extension is a definite welcome addition.