One of the best! Rated 4 out of 5 stars
This is one of THE BEST extensions for the best browser around. I highly recommend it to all my FF using friends. You can configure it to use with just about anything that has a search text box. Here's what I currently have:
and sometimes I'll swap Wikipedia for Dictionary:
The ONLY reason I didn't give this extension five stars is because you cannot determine how many options/"dictionary" searches you'd like to have. IOW, instead of having just 4 searches I'd like to have 5 or 6. I haven't dabbled in writing extensions for FF so I don't know how to edit the source code to do this. It would definitely be a nice feature the author could have have for the end users though. All in all, a great FF extension!