I just bought a macbook and want to upgrade the memory to 4gb ASAP. I was wondering if there was any recommendations about what brand to get? and maybe where I can purchase it? I just want to get something that is compatible and will give me the best performance. Thanks!
Depends where abouts in the world you are, there are a few places listed in this post. You will be looking for ram that is DDR2 PC2-5300, for example the Crucial UK page has this ram, which is currently very decently priced.
Many sites have a memory selector feature where you tell it the manufacture, then make, then model and it brings up the correct ram. But feel free to post links incase you are not sure.