Twelve South MagicWand
Twelve South's MagicWand is one of those products that does one simple job and does it well. It's a small, extremely light (as in, lighter than two AA batteries) polycarbonate halfpipe that you snap an Apple Wireless Keyboard and an Apple Magic Trackpad into, side-by-side, combining them into a single unit.
Whereas you previously might've had to reach across the desk from one device to the other, the MagicWand keeps everything nice and tidy and unified. You can also put the trackpad on either side of the keyboard you like. For example, you could attach it on the left side and still use a Magic Mouse on the right, if you want the best of both worlds.
Get the MagicWand for $30 on Amazon.