The Mozilla Foundation tracks its bugs via the Bugzilla tool (another Mozilla product). Over the time that I've spent using Firefox, I've opened a few bugs. I'll list them here individually: 248350, 248352, 292498, 296266, 296399, 296462. Here's a general query: here.
Most users probably don't realize that anybody can open bugs in this fashion, track the progress of fixes and talk with developers in bug reports. Depending on the area under which your bug is found, you may see "instant" response (i.e. within a few minutes a developer may offer a fix) but for others response can be quite a bit longer. It all depends on priority, of course.
Anyway, all it takes is to sign up for a free account (available from the link above but if that link seems to hang you can just go go here). The only problem I see is that the Bugzilla database queries are too slow for mass consumption.