I know this has been mentioned many times in the threads, but I don’t think it has ever been mentioned here. So here it is.
William Whitaker’s WORDS Dictionary. An online Latin Dictionary. You can also download it onto your computer.
http://users.erols.com/whitaker/words.htm
yay!
It has a pretty impressive vocabulary, but more importantly, it can recognize a word by its root… even if you don’t know the noun nominative/verb stem. It is also very knowledgable about archaic forms that your typical textbook wouldn’t inform you about (but certainly A&G would).
I just went to find this for my new computer and the link to the file (on the site) does not work! Apparently the exe file is missing. Does anyone have a copy of it handy or know where I can find one? I found some old versions on another website but would like the newer one. 
Did you ever get a good working copy?
I just downloaded it from that same site, and it appears to work fine. I didn’t even notice there was an updated version that allows you to toggle between Latin-to-English and English-to-Latin. Pretty nifty!
I also have the older ver 1.97 (from way before Jan 19, 2005) if you want a copy of that one.
I have tried the Windows version. And the toggling between E-to-L and L-to-E is enabled by tilde(~)s, not carot(^)s as the online manual says. ~e and ~l both in interactive and command line operations.(Anyway it’s a great improvement. Or rather, another great software.) What about the Mac OS version?
The Mac version has a graphic interface where you can click on ‘Latin to English’ or ‘English to Latin’.
The interface is simple, but effective.