Mark, 

hard maple is excellent for a Moxon vise and very traditional but you can use other close-grained hardwoods, like beech.  Moxon vises are useful and fun to make and there are lots of different screw mechanisms out there. I like the kit  from Tools For Working Wood in New York and you can see an example in the bench room and the Studio.  The kit from Benchcrafted is beautifully made but twice as expensive, so it depends on your budget. You can also make one by buying your own handles and acme thread rod, similar to the ones that Ken Hall and Dennis Dolph made recently for the shop. The wood and mechanisms for those were donated but you can get parts at Grainger, I imagine.

You should try the various examples and see what you like, in terms of mechanism and size. Remember, the vise both holds a board and improves the sawing ergonomics: you are basically trying to bring the ideal sawing level (just above the vise) high enough above your hand-tool bench that your sawing forearm is roughly parallel to the floor, which generally means a vise 4 or 5" high, and then wide enough for drawer sides, etc. If you do make one, we have found that the extra shelf in back to help support your boards is a pretty good idea. It makes the vise heavier but easier to use for dovetails.

You can drop by the Studio when I'm there  and I'd be happy to demonstrate.

Tim