The iMac was built to be pretty. So why not sidestep the difficulty of recycling e-waste by making discarded iMac carapaces into something attractive for the home? Jake Harms had the clever idea to make them into aquariums, for "Mac and fish enthusiasts worldwide." The cases for his pre-made iMacquariums are sourced from recyclers, so you're not exactly saving a computer from the dump, but he also offers a kit for building your own.
