I really like what my ZDNet colleague George Ou has done with this custom-built dual-core VESA Stand PC. Personally, I belong in the “hide it in a cabinet or under a desk” school, but that’s probably because I never really got into wood shop.
It could probably use a little finishing work, but all in all, a fine bit of handiwork, and the commenters seem to agree.
Ed Bott (@ wordpress.com) 
The wallpaper he used is also quite an attention-getter (or so says the Japanese art fan!)
Actually, that’s one of the default wallpapers from Windows Vista. You’ll find it under the Paintings group.
But if you hide it under the desk, you’ll need to power it and cable it separately from the LCD. The all-in-one design doesn’t take any more desk space than just the LCD by itself and requires no modification to the wall or the desk and it’s transportable. You just feed it with a power cord and you’re up and running.