A Introduction to Zope bug-squashing party is now supposed to happen on IRC the last friday of every month, since about april 2004. ChrisW? is chief evangelizer, and announcements of bugdays are usually sent out with little notice, so as to keep the developers on their toes.
It's held in the #zope-dev channel on irc.freenode.net. The idea is to focus a lot of energy on the ZopeCollector in a short time. Hopefully for good. You can help a lot without knowing anything about python code. Just show up.
Next bug day is not yet announced. Be there!
Or maybe you were looking for BugTrackers.