A simplified version of kparlin's laptop HDD adapter. Much less plastic used, and only a single print, instead of 5.
**v3- Made the holes a bit bigger and walls a bit thicker. Also replaced the 3 cross-members with just one, because it was taking a long time to print the 3 thin cross-members.
Update 8/10/11 Added adapter that just uses bottom screws of the 2.5 inch drive, and no crossmembers. This design also has the middle mounting screw often found on 3.5 inch drives and cases.
This is a large print, so be aware that warping might be an issue.
The adapter-to-case screw holes need to be tapped, which should be easy enough by just screwing in some screws into the holes. Go slowly and back out often when it gets too tight, or else you'll probably separate the layers. Do this before trying attaching the HDD and putting it into your computer.