GS1 sites, which give UPC information to the public. We're not certain how reliable the database is, so we're tacking "rumor" on this story for now. Interestingly, we did test various UPCs we had lying around, like the one on our copy of BioShock (710425299636) and another on a carton of Half & Half (075457427007), and all showed up correctly -- the website claims not to allow user generated data.
If the PS3 40GB UPC listing is correct (we're attempting other avenues of verification at the moment), it would be another log on the rumor-fire that just won't die. The key "feature" of the 40GB PS3 model would be its alleged $399 price tag, bringing the system into much more financially-friendly waters, and hopefully increasing system sales. If this UPC code holds up, it'll be hard for Sony to keep a lid on the 40-gigger much longer, but for now it's still very much in rumor territory.
Update: Engadget's got word of the 40GB model appearing in Best Buy's internal inventory.
Update 2: PS3 Fanboy shows Play.com has it now too.
[Thanks J. Jenkins]