This would be a perfect fit for a group that meets together to work on hacking skills (
http://www.meetup.com/skillhack/). They get together a couple times a month at the Miller Entrepreneurship Center in their startup incubator space to work on improving development, design and business skillz.
I helped organize the first one, but Seth Jenks, who is doing the organizing these days, would possibly love to help. There's a decent chance he'd lend his awesome design skills to the cause as well.
So, if you think this would be a great learning opportunity and collaboration, suggest it as a meeting with Skillhack. There are people in that group with design and business skills who want to learn to program (as well as programmers who want to learn businessy/design stuff). By getting people in the same room working on a project together, teaching each other stuff, everyone benefits. The next meeting is on the 26th of this month.
The format is very similar to what David suggested. A bunch of people get together and hack on stuff for a few hours. Sometimes people pitch in for lunch.
A handful of URUGers are involved in Skillhack already.
Just my $0.02.
Also, if you'd rather not do it with Skillhack, the people at the Miller incubator are really good to work with and would likely give you space to have a hackfest (depending on their calendar). Ping me if you want contact info.
peace out.