I bought my 8GB kit from data memory systems which had Samsung branded modules that looked almost identical to the modules I pulled from my MBP. Same ID sticker etc.
I decided to go this route as should my machine ever fail and need to be replaced by apple (happened before) I know the replacement Mac will have equal or better value.
I had an iBook G4 which was max factory specced aside from the ram which I installed a 1GB module bringing it to 1.5GB. Long story short, Apple replaced my iBook with a brand new CTO MacBook (1,3 Santa Rosa @ 2.2Ghz) which Apple kindly supplied me with 4GB of ram.