This deal has ended.
Dell Small Business has their Vostro 200 Desktop for only $499 after $300 instant savings. This is well-configured, pretty fast machine and relatively inexpensive if you want to upgrade (just scroll across the component icons at the middle). It comes standard with a 2.2GHz Intel Dual-Core processor, 2GB memory, 80GB hard drive (upgrade to 160GB for $30), 16x CD / DVD burner, Windows XP or Vista Home (I recommend XP, Vista isn't perfected yet), and a 20" flat-panel monitor. Shipping is free.