Dan's Data has put up a review on the Lian Li drive mounts
Various frugal PC users have added more drive bays to their box with home-made panels and bars and baling wire and chewing gum. Lian Li have a couple of products that make the job easier.Read more
Their MF-20 and MF-30 kits let you add two or three more 3.5 inch bays, respectively, to most tower form factor cases. They're quick to install, and they look pretty good, too.
And they're even cheap.
Well, by Lian Li standards, anyway.