Best Buy's trade-in program, it appears the service is actually provided by a company called Dealtree.com, which seeks to offer "fair value" for old electronics. For example, the trade-in price for a Gamecube in good condition is $25; if that seems acceptable all the customer has to do is print out the pre-paid shipping label, send it to the company and in seven business days it'll send a Best Buy gift card for the value of the trade-in.
Dealtree.com apparently provides its services to a variety of retailers. It appears trade-in values are universal as a very quick check using the same parameters on the Circuit City version yielded the same trade-in value as with Best Buy. A sterile alternative to eBay or Craigslist for those looking to unload old consoles.