report of bugs other issues

Ok, I'm getting to really like Firefox, using it on RH Linux 3.0 at work 
and my couple XP boxes around here. I have found a number of different bugs 
and problems with certain pages. Is there a good place to report these? Or 
a bugzilla like site that I can first search to see if it was identified 
already, then if not, some where to post it to?

Just wanting to help improve Firefox...

-grant