If you love macs and you love fish, here's a great project to make. A Macquarium is a fishtank made out of old compact mac cases. The "final upgrade", heh!
Construct A MacQuarium! great instructions with notes by the author on their construction experiences.
Dan's MacQuarium has a great pictoral instruction guide.
Aleks Oniszczak's MacQuarium Scroll down a bit for a great story on how Aleks built a MacQuarium. Also has nifty ideas such as making the mouse control the tank lighting, etc.