Will upgrading to 4GB RAM on a white MacBook work? I've seen discussions about upgrading memory but it was only for the MacBook Pro. I have a white 13" MacBook with 2GB memory, I'm considering about upgrading the memory to 4GB.

Is it possible to upgrade the memory from 2GB to 4GB with the white MacBook (late 2009)?
All white Macbooks can certainly be upgraded to 4 and -in some cases- 6GB of RAM.

Depending upon your model, you should check OWC's Memory Upgrades and go from there. I believe other vendors (Crucial, Newegg, etc.) will have similar pages with similar info (and similar prices). I've brought different memory upgrades from OWC and never had a single failure so far. 

I have an old Macbook 4.1 White Core 2 Duo 2.4 and can go up to 6GB. So best thing to do is check your exact Macbook model and see what they offer.