Extreme Tech article on building a MCE
Another article on building a Media Center, this time from Extreme Tech, Build Your Own Windows Media Center PC
$549 refurbished living room PC
Computer Geeks, Gateway Cel 2.6GHz 256MB 80GB CDRW/DVD w/XP Media Center2004 for $549.
Buyer beware, Gateway discontinued this box fairly quickly after introducing it. However, I have a Gateway 901x at home and it works just great (though mine is a P4 3.0GHZ, 512MB 200GB w/Media Center 2005). Had I seen this prior to going off and building my own, I might have bought it upgraded a few components (added more ram, a bigger HD, upgrade to 2005).