UPDATE (2005/01/21): See also, my newer post containing the entire service PDF of how to take the Mac Mini apart, including high-resolution photos and a list of the required tools. — Nice! 😃
Somebody leaked me this video, demonstrating how to crack-open the Mac Mini's casing and expose its internals. — I'm not sure if it's legal for me to post this or not, but here it is! (Until I hear differently, this will remain available here.)
I'm not responsible for any damage to your Mac Mini, so please take care. This is purely for instructional purposes only.
AppleInsider has additional information on the Mac Mini's hardware, in case you're planning on attempting any upgrades. — Macworld also has a quote from Apple (in an article comparing the Mac Mini with a similar Dell PC) that, as long as you don't break your Mac Mini while working on it, it is still covered under warranty:
The Mac mini includes a video card with dedicated memory, and you can upgrade the Mac mini’s RAM to 1GB—contrary to rumors around the Internet, Apple has told Macworld that you can even do it yourself without voiding your warranty “unless you break something when you open it.”
UPDATE: Welcome, fellow Slashdotters!
Here's another article that I wrote about the Mac Mini: “Mac Mini vs. Airport Extreme/Express?” — Check it out! 😎