Ebay. I got a 512x2 1-gig kit for $215+shipping, there are people who landed even better deals. It's really the only place right now where you can expect a price under $250 for 512x2 kits, as well as great prices on other sizes of mac pro RAM. I'd recommend if you're looking for Mac Pro RAM you check Ebay first. The profiteering that's been going on at Crucial and other suppliers is disgusting (heatsinks cost $100 extra? give me a break), stick it to them by not buying from them at all. Try searching "fb-dimm" or "mac pro ram" to find some results. I'm glad I didn't go for Crucial.