I got 4 gigs for my MacBook (q4 2007) a few weeks back. Its well worth it. I got the crucial ones direct from their website. I have noticed a huge improvement. Especially with Parallels. I set XP to have 1.5GB RAM and 64MB Graphics and it works really well. No lagging at all.
Highly recommend it, especially from crucial - it took a day to arrive. (UK)
Highly recommend it, especially from crucial - it took a day to arrive. (UK)