Geeks.com offers the refurbished Apple Mac mini Intel Core Duo 1.83GHz Desktop, model no. MA608LL/A, for $349.99. With free shipping via coupon code "FREESHIP", that's $392 under the lowest total price we could find for a new one. (However, it's rare to find a factory-sealed version of this older model.) It's also tied with a June 2009 mention (of a faster model) for the least expensive Mac mini we've seen. Features include an Intel Core Duo T2400 1.83GHz dual-core processor, 512MB RAM, 80GB hard drive, SuperDrive dual-layer DVD burner, AirPort Extreme 802.11g wireless, Bluetooth, and Mac OS X Tiger (10.4.7).
A 90-day Geeks warranty applies.