Corsair XMS2 4GB (2 x 2GB) PC2-6400 Dual Channel DDR2 Desktop Memory for $24.80 shipped after this $20 rebate. Here is a screenshot for your reference. For the technically inclined, this set of RAM has a voltage specification of 1.9v and operates at 800MHz with 5-5-5-18 timing. Most places have it for over $35 after the same $20 rebate.
This deal has expired. Congratulations to those who were able to get in on it.