I don't typically advocate products in this blog, but I have very high praise for Ergon's bike grips. A few weeks ago I started to bike commute to work several days a week (about 9 miles, on and off-road paths). Being familiar with Ergon's products through their exposure in design awards, I purchased the GC2 grips as my first aftermarket product.
From my personal experience, the grips are a clear improvement over traditional cylndrical ones in that they provide significantly more surface area for the hand to rest on, particularly the lower palm. Ergon's site provides some nice schematic Flash animation of the ergonomic advantages, from both angular deviation and surface contact perspectives. I was also satisfied with the smooth material finished that doesn't leave depressions on your skin from long duration rides. So real-world approval from a Certified Professional Ergonomist (and cyclist).
Ergon also designed an interesting backpack that uses a ball joint to separate the backpack straps from the backpack body. This allows the user to move more freely without the backpack slipping (see ergonomic explanation here).