8GB (4GBx2) Team High Performance Memory RAM Upgrade For Lenovo ThinkPad T510 Series W500 Series Laptop. The Memory Kit comes with Life Time Warranty. at Amazon.com
OFFTEK 4GB Replacement Memory RAM Upgrade for IBM-Lenovo ThinkPad W500 Series (DDR3-10600) Laptop Memory at Amazon.com
Best Buy: Lenovo 15" ThinkPad Notebook 4 GB Memory 320 GB Hard Drive Black R500-2.26C2D-4-320-D-7P