CompUSA.com is offering the OCZ SLI-ready, dual channel 4GB (2x 2GB) DDR2 memory kit (model no. OCZ2N800SR4GK) for $39.97, which is already the lowest price we could find on this memory kit by around $4, and until 12/31/08 use this mail in rebate offer to drop the price down to $9.97.  Shipping rates start at around $7 and vary by your location and method of delivery.  Sales tax applies for residents of Florida, Texas, North Carolina, and Illinois.
 

The OCZ 4GB 240 pin, dual channel DDR2 memory kit includes two 2048MB units clocked at 800MHz.  Also, it is instilled with a NVIDIA XTC heatspreaders, which is designed to give you unparalleled heat dissipation.  It is backed by a lifetime warranty from OCZ with toll-free technical support.