I am selling 8GB of genuine Apple certified memory. They are two 4GB sticks and will work in the following machines:
MacBook - Any Unibody model after 2008 (Except new Retina model)
Mac Mini - Any model from 2009 or later
I am not sure what other models might use this memory but you can research and find out.
This is the perfect way to speed up an aging system that is starting to run slower after time and newer memory hungry OSX installations.
I would be happy to install the memory for you as well. I am located downtown.