We'll do a testday on it soon, I just wanted to encourage anyone interested to start looking at it now :-)
How can you help? Like all Mozilla projects, there's always a list of fixed bugs/features to verify, as well as a good amount of exploratory testing. For examples of the kinds of things we'd test for, check out a couple blog posts by yours truly: part 1, part 2.
What makes testing this particular site a bit unique is that Mozilla Reps is made up by a community committee, so most of the functionality depends on being a bonafide member; for testing purposes, we can bypass the usual application form, by making you a "vetted 'Reps' member" (though, of course, we encourage you to apply for real!)
Here are some more general resources to help get you familiar:
* Mozilla Reps wiki page, for general information/an overview
* Mozilla Reps "Website" page, for specific website-release information
* a list of open bugs, so you don't file duplicates
* all Resolved FIXED bugs needing verification
And, lastly, a link back to the Web QA homepage, in case you have any further questions, about this or any web-testing project(s) @ Mozilla!