G.Skill 8GB DDR3 PC3-10600 1333MHz CL9 NT Series Desktop dual channel memory kit (2x4GB) at Amazon.com
What Is Dual-Channel Memory?
Vaseky Knight Game Memory Ram DDR3 16GB(2*8GB)Kit Support Dual Channel 1600MHz Chips Unbuffered DIMM DDR3 PC3 12800 for Intel AMD System Desktop Memory Model with Cooling Vest - Newegg.com
Corsair XMS3 4GB (2 x 2GB) Dual Channel DDR3 CMX4GX3M2A1600C9