One thing I would like to see is an entire area of "driver development" tutorials/samples for Haiku/BeOS. This is one area where Haiku truly needs more help if it wants to be a truly viable solution in the future. The plethora of open-source drivers for other OSes should serve as decent "reference drivers" for Haiku, and maybe someone with the knowledge can put together some "driver porting" information to help potential driver-writers to "port" driver code from other platforms to Haiku.
The thing is that the driver model is going to change. That's what I've been hearing for a while now anyway. The only guy that probably knows what the new driver model is going to look like is Axel, and he's doing a lot of other things that are probably more important than documenting the new driver model for now (like being on holiday in France ;-).
This sort of creates a strange situation where it's probably useless to document the new driver API since Haiku's not for general use anyway, and it's useless to put a lot of effort in documenting the old driver API since that one's going to be obsolute when Haiku releases in 2012. Probably the best way to go about this is that someone spends some hours collecting the resources that are currently available and creates an index of them. Perhaps it's even time to start documenting some of the functions that are going to be in Haiku and that are also on BeOS to aid in common driver operations.
But I do think that waiting for things to stabilize is probably the most efficient way to do. Guys like Chris who want to do things now can get personalized advice via lists like bedrivertalk :-)
Niels