As part of my Matasano internship, I've been working on a patch to NSS (Mozilla's crypto library, used by both Firefox and Chrome for TLS) that will give the necessary hooks needed for browsers that use NSS to implement TACK. I'll hopefully be submitting that for review soon (you can see it on bugzilla[1] and fresher in-progress GitHub[2]).
At this point, it mostly makes sense for me to finish that (though I'll have a lot less time when I go back to school, so there might be some work that needs to get done when the review comments come back that I can't get to for awhile, so someone to power that to the finish might be helpful).
But once that's in, we'll need to work on getting patches into the Firefox and Chrome that actually integrate TACK. There's also some other work to do, especially for some other longterm ideas we have (eg. securing communication between mail servers with TACK).
If you're interested in helping, either email Trevor (email is on his website[3]), or email me (danielj@matasano for the next week, personal email in my profile).
1: https://bugzilla.mozilla.org/show_bug.cgi?id=905848