Yeah yeah, I know this question has been asked before, but that was a month ago! So now it's my turn.
Answers:
ImageZoom: you can enlarge photos by holding down the right mouse button and scrolling up or down.
FlashBlock: automatically blocks all the flash on a site and replaces it with a clickable button.
TabPreview: opens up a thumbnail of a tab when cursor is hovered over it.
Adblock
faster fox
My Favourite has got to be My del.icio.us Tag. :)
I have always used the adblock extension since before version 1.0.
I like the new Forecast Fox
I like NoScript, but I have problems with it every now and then.
I like the new Anti-Poll 2006 extension -- it subscribes pollers to various nasty porn sites when they don't put their questions in the poll category.
UPDATE:
You don't need to be perfect, just don't be a tool.