Patriot Viper Viper 3 8GB PC3-12800 DDR3 Desktop Memory for $19.99 shipped after a $15 rebate.  Here is a screenshot for your reference.  For the technically inclined, this dual channel RAM operates with 9-9-9-24 timing at 1.5V, which makes it compatible with most standard systems.  Most places have this set of RAM for about $42.