MegaMacs.com offers the used Apple iMac Intel Core 2 Duo 2GHz 17" Widescreen All-in-One Desktop
, model no. MA590LL/A, for $579.99
. With $29.85
for shipping, that's the lowest total price we could find, although we saw this iMac for $98 less in October (since expired). It features an Intel Core 2 Duo T7200 2GHz dual-core processor, 17" 1440x900 widescreen LCD, 1GB RAM, 160GB 7200 rpm hard drive, dual layer DVD burner, 802.11g wireless, Gigabit Ethernet, Bluetooth 2.0+EDR, iSight webcam, and more.
Update: The OS is not specified and a 30-day MegaMacs.com warranty applies.