I own a Macbook 5,1 (unibody), last week I bought 4gb memory frow OWC. Yesterday, I tried to install it and the 204 pin kit got jammed. Since, I didn't want to damage the RAM or worse the Macbook itself, I brought it to an Apple Store for repair. Today, while reading the Mac's instruction booklet, it says that I should be using 200 pin PC3-8500 DDR3 1066MHz SDRAM while everywhere on the internet, it says that this computer uses 204 pin PC3-8500 DDR3 1066MHz SDRAM. Now I wish I haven't caused any permanent damage to my MB by forcing 204 pins into 200 pin slot!
The 200 pin memory listed in the manual is either a typo, or a "nominal" number. 200 pin RAM is DDR2. Your Mac uses DDR3, so the 204 pin is in fact what you need. There's no such thing as 200 pin DDR3. Sites that list such an item are mistaken. Search the Crucial or Kingston website for the proper memory for your Mac and you'll see it lists 204 pin DDR3 as the correct memory.