Amazon.com: Timetec 8GB KIT(2x4GB) Compatible for Apple DDR3 1333MHz PC3-10600 for Mac Book Pro (Early/Late 2011 13/15/17 inch), iMac (Mid 2010, Mid/Late 2011 21.5/27 inch), Mac Mini(Mid 2011) RAM Upgrade : Electronics
OWC a la Carte Upgrades for iMac, including eSATA, Memory, SSD option
Install memory in an iMac - Apple Support
NEMIX RAM 16GB (2x8GB Upgrade) DDR3-1333 PC3-10600 204-Pin SODIMM Memory for Apple MacBook Pro Early/Late 2011, iMac Mid 2010 27 inch 4-Core, iMac Mid 2011 21.5/27” , Mac Mini Mid 2011 at Amazon.com
Install memory in an iMac - Apple Support
iMac RAM for Model 11.2 to 12.2 | DDR3-1066MHz | 4GBx2 | MacMemory.com
8GB 2X 4GB Memory Compatible for Apple iMac Core i3 i5 i7 Mid 2010 DDR3 PC3-10600 204 pin 1333MHz SODIMM RAM (PARTS-QUICK Brand) at Amazon.com
A-Tech 8GB RAM for Apple MacBook Pro (Early/Late 2011), iMac (Mid 2010 27 inch 4-Core, Mid 2011 21.5/27 inch), Mac Mini (Mid 2011) | DDR3 1333MHz PC3-10600 204-Pin SODIMM Memory Upgrade Module at Amazon.com
Is it worth it to upgrade RAM on Mid 2010 21.5 iMac? | MacRumors Forums
Is it worth it to upgrade RAM on Mid 2010 21.5 iMac? | MacRumors Forums
Memory RAM Upgrade for Apple iMac 21.5-inch Mid 2010 4GB DDR3 SODIMM | eBay
A-Tech 32GB (4x8GB) RAM for Apple iMac (Mid 2010 27 inch 4-Core, Mid 2011 21.5/27 inch) | DDR3 1333MHz PC3-10600 204-Pin SODIMM Memory Upgrade Kit at Amazon.com
CMS 16GB (4X4GB) DDR3 10600 1333MHZ Non ECC SODIMM Memory Ram Upgrade Compatible with Apple® iMac Core I3 3.06 21.5-Inch (Mid-2010) - A28 at Amazon.com
Adamanta 16GB 4x4GB Apple Memory Upgrade for Mid 2010 iMac 21.5" and 27" DDR3 1333Mhz PC3-10600 SODIMM 2Rx8 CL9 1.5v RAM