This is my current keyboard/trackball setup. I have been tweaking my configuration for a number of years and this is the most comfortable option I have found for my particular body ratios. I think the best layout may vary somewhat from person to person.
The keyboard is a Kinesis Freestyle 2 (also referenced by other folks in this discussion). I find the regular one with the 9 inch cord is too short for the separation I need, so I have the 20 inch cord option. Come to think of it, I would be totally screwed if these went out of production, so I'm going to go order another one right now to keep as a backup. The trackball is a Logitech Cordless Optical Trackman, which is no longer made, and I wish I had a few of these stashed to use for backups.
That's pretty cool. I've sometimes imagined a programmer presenting things and instead of him fiddling with a laptop (MacBook..) from time to time, he manipulates a keyboard attached to his thighs or hips while using the projector as the monitor. Almost "cyborg"-like or really geeky, depending on how you look at it... :-)