This is cool...but it also tells me that I can't do anything for Mozilla. And I find that unfortunate.
I wish open source projects would openly solicit help with things like
1) Writing tests
2) Writing documentation and tutorials
3) Bug finding and reporting
4) Bug report maintenance and management
5) Porting to new platforms
Not everybody is capable or willing to work on the stuff that devs find glamorous...and a project has no chance of real success without the things I mentioned.
My attempt at providing helpful links for your requests (and ignoring the problem of whatcanidoformozilla.org not having this stuff):
1. There's probably better resources for QA for the browser and other Mozilla projects, but the WebQA is awesome at working with contributors and getting them to help on real projects (I've worked on website releases where 100% of our QA and bug verification was done by contributors): https://quality.mozilla.org/teams/web-qa/
4. I'm not sure about this one; A lot of triage happens by the teams working on a specific project, as managing these bugs requires a lot of domain knowledge. Closest link I could find was how to contribute to Bugzilla itself: http://www.bugzilla.org/contribute/
5. This looks like an outdated page (updated February 1st, 2012!) but it has some info on ports. I would recommend joining the #developers channel on the Mozilla IRC and asking around. In general the larger IRC channels will help point you in the right direction.
I wish open source projects would openly solicit help with things like 1) Writing tests 2) Writing documentation and tutorials 3) Bug finding and reporting 4) Bug report maintenance and management 5) Porting to new platforms
Not everybody is capable or willing to work on the stuff that devs find glamorous...and a project has no chance of real success without the things I mentioned.