Other World Computing offers the used Apple Mac mini Core 2 Duo 1.83GHz Desktop, model no. MB138LL/A, for $199 with free shipping. That's $400 off and tied with our mention from two weeks ago as the best price we could find. It features an Intel Core 2 Duo T5600 1.83GHz dual-core processor, 1GB RAM, 80GB hard drive, CD-RW/DVD combo drive, AirPort Extreme (802.11g wireless), Bluetooth 2.0 + EDR, and Mac OS X 10.4.11 (Tiger).
A 90-day Other World Computing warranty applies. Additionally, note that this unit doesn't include the original OS X install disc.