How To Upgrade/Replace Mid-2011 iMac 21.5" Hard Drive To an SSD! - YouTube
How-To: Now's the right time to swap your old iMac's hard drive for a fast new SSD - 9to5Mac
Amazon.com: OWC Internal SSD DIY Kit For All Apple 21.5" iMac 2011 Models w/ Tools : Electronics
iMac Intel 21.5" (Mid 2011) Dual Hard Drive Kit
OWC DIY Drive Upgrade/Install Kits for Apple iMac Models
Amazon.com: OWC SSD Upgrade Kit for 2011 21.5-inch iMacs, Mercury Electra 250GB 6G SSD, 18" SATA III 6Gbps Data Cable, Installation Tools and iMac Screen Adhesive Tape Set : Electronics
OWC DIY Kit for 2009 - 2011 27" iMac optical bay:... at MacSales.com
OWC Internal SSD DIY Kit for All Apple 27" iMac 2011 Models
Amazon.com: OWC Data Doubler Kit for 2009-2011 iMac, 1.0TB 3G SSD with Mounting Solution and Toolkit : Electronics