Upgrade your iMac's RAM in less than 5 minutes - YouTube
8GB PC10600 DDR3 1333MHz SO-DIMM Memory Compatible with 2011 MacBook Pro, Mid 2010/2011 21.5" & 27" iMac Models, 2011 Mac Mini (OWC1333DDR3S8GB) at Amazon.com
A-Tech 16GB (4x4GB) RAM for Apple iMac (Mid 2010, Mid 2011, Late 2011) | DDR3 1333MHz PC3-10600 204-Pin SODIMM Memory Upgrade Kit at Amazon.com
Amazon.com: Timetec 16GB KIT(2x8GB) Compatible for Apple DDR3 1333MHz PC3-10600 CL9 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) MAC RAM Upgrade :
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
32.0GB OWC Memory Upgrade Kit For 2010-2011 Apple iMac
iMac Mid-2010 27 inch (A1312) SSD and RAM disassembly and upgrade - Much FASTER! - YouTube
Install memory in an iMac - Apple Support
Amazon.com: Timetec 32GB KIT(4x8GB) Compatible for Apple DDR3 1333MHz PC3-10600 CL9 for iMac (Mid 2010 27 inch, Mid 2011 21.5/27 inch) SODIMM Memory Module MAC RAM Upgrade for iMac 11,3 / iMac 12,1 / iMac 12, 2 : Electronics
Is it worth it to upgrade RAM on Mid 2010 21.5 iMac? | MacRumors Forums
How to upgrade RAM / Memory on a 2010 iMac Core i3 i5 i7 (21.5in & 27in) - YouTube
iMac RAM Models 11.3 (i5 and i7 only) to 12.2 (8GBx4) | MacMemory.com
Memory RAM Upgrade for Apple iMac 21.5-inch Mid 2010 4GB DDR3 SODIMM | eBay
Adamanta 16GB 4x4GB Apple Memory Upgrade for Mid 2010 iMac 21.5" and 27" DDR3 1333Mhz PC3-10600 SODIMM 2Rx8 CL9 1.5v RAM
Timetec 8GB KIT(2x4GB) Compatible for Apple DDR3 1067MHz / 1066MHz PC3-8500 CL7 for Mac Book, Mac Book Pro, iMac, Mac Mini (Late 2008, Early/Mid/Late 2009, Mid 2010) SODIMM Memory MAC RAM Upgrade