Fernando over at the Inq-well's got a list of his most-used extensions up for your perusing pleasure. If you're a Mozilla user, you'll definitely want to give this list the ol' once-over.

"Here is a personal list (in no particular order) of the 'must have' extensions that can be installed on top of both Mozilla Suite 1.7.x and Netscape 7.2. I hope some of you find them of interest."