Caleb has a post up on the SIRT pistol, a dedicated dry-fire handgun that shoots a laser out the barrel whenever the gun is "fired."
While this seems like a good way to train, I'd be afraid that it would make me look for the laser and not call my shots - see the sights, take the shot, and move on knowing that I'd hit the target.
I dry-fire with a trigger kit from Southwest Shooting Authority. The kit replaces the trigger for your Glock, and automatically resets. Print out some 1/3 scale targets (available here), post them on your basement/garage wall, and dry-fire away.