Memory upgrade for MBP
The Crucial kit is one of the better ones out there.  I've used their modules in the past.  However, on my new MBP, I decided to get the 8 GB from Apple.

I'd go with the Crucial if you want good quality and great value.

Here is a video showing installation
http://www.ramfor.com/ram-memory/apple-macbook-pro-early-2011-crucial-memory-upgrade/