While slightly different, not entirely focused on the tutorial/how to side of things,
FRC Designs has recently become the main archiving of CAD files and other documentation for public viewing.
I agree that tons of manpower is thrown at solving the problem (game) each year, but think that most teams find it difficult enough to work within their own team - now try adding the dynamics and organizational differences of one, two, or ten additional teams and it potentially becomes a nightmare. Yes, there are many small "alliances" or partnerships between teams, but to what extent is exact CAD files (or similar) shared? I have no idea.
I do like the idea of getting some tutorials up and running for the new students and mentors, but not sure what the best vehicle is for this. We typically reference the ones posted on
Team 254's resources page as a good starting point. Another good mechanical tutorial location is
Team 973's RAMP video series, I would put some of these a bit above beginner level from a design standpoint - but easy enough to understand.
I am a firm believer that sometimes the best tutorial for the off-season is figuring it out yourself, or as a team. Find a design problem and work through the process of solving it. Sometimes I feel that following a tutorial on how one person/team thinks a problem should be solved is detrimental to what the purpose of the training. Sure if you want to learn CAD you can follow click-by-click instructions; but if you are trying to develop some sub-system, you may just want to be able to reference how it has been done before. I would be very cautious of just redoing what someone else has already done - fundamental design understanding is very easily lost in this method.
I think I got a little off topic, but hopefully this answers some of your questions.