Just appeared in the Apple refurb section this morning. I'd wager that it's left over stock since now the smallest iMac screen size they sell is 24". Why do I think it's hot? Because it's the cheapest I can find this item!
20-inch glossy widescreen display
320GB hard drive
8x SuperDrive (DVD±R DL/DVD±RW/CD-RW)
NVIDIA GeForce 9400M with 256MB memory
Built-in iSight camera