That's great!
GameMaker (neighborlee on IRC) is busy doing some of the modeling preparation, so I think it would be best if you discussed with him about what would you can take care of.
If you can make it on IRC, there's quite often someone online now
I've shared set up a dropbox folder for preliminary work, so if anyone needs access to see and/or dump stuff in there, give me a shout and I can set you up. For the actual game development, I'm thinking that we can put it on either google code, or github or something. I'm currently working on a couple of framework things (extending what I did in the tutorial series for a little more flexibility) and that's in a personal git repository, so for me, github would be easiest, but if people have a preference, I can put it anywhere.
I have no idea how much more preparation I can do this week, as I think I'm going to be working late... What I already have is a character (penguin "borrowed" from a CC blend on blendswap) which technically moves around, although you can't really tell much as there are no points of reference. I also have a post processor which can be enabled/disabled (and does so automatically if it's not supported) which currently just does fogging to blue. I think that's about it. I've done a little extension to the GameClock, allowing timefactors, and an easier interface for multiple clocks (so you can trigger things off a UI clock which you can keep running constantly, then have a main clock which we can slow down maybe?) and a couple other little tweaks which "might come in handy"
What I still want to do with the stuff for the weekend is make a generic statemachine which we can use for game states (assuming someone fancies making a menu... maybe a 3D menu with penguin going through "gates"?) player state for character etc. I also want to dump a couple of random objects into the world and try and get a very basic swim-control system going.
This weekend, which has been scheduled for the dev jam, what I intend to do is create a shader for the water (ideally above and below, potentially different shaders, not sure yet) and a post processor for the underwater view (maybe a bloom shader which fades for a few seconds after you stick your head above water?) Create more extensive control mechanics. Maybe make an interaction system.
I think with those few things I'll already have my work cut out for me, but it's a decent goal. If we get more people volunteering for code work, we can maybe add some more features