Sort of. It's that drop down thingy, and there are several others you can add from the firefox central site (I like M-W.com's dictionary instead of dictionary.reference.com, so I use it).

However, it's not really the full blown google toolbar. G's toolbar add's a lot of simplistic things; "Blog This!" button for Blogger users , highlighting search terms on the page, page ranking statistics, some other things.

However, I am in the midst of troubleshooting a problem. Every post I have made here, since installing it (and I tried it three times, before switching to Internet Exploder) has caused a crash. The Java spell checker (which I don't use...imagin taht) and the G toolbar don't play nicely, I'm guessing. Unsubstantiated at this time.