High bandwidth, low power, reasonable price?
http://www.micron.com/products/hybrid-memory-cube
http://ra.ziti.uni-heidelberg.de/cms/research/recent-research-projects/openhmc
http://forums.xilinx.com/t5/Xcell-Daily-Blog/Open-source-AXI4-compliant-memory-controller-for-the-Micron-HMC/ba-p/547195