Not the memory in my brain, mind you. That's pretty lousy. The RAM that I ordered last week arrived yesterday while I was at work. The price difference between various vendors was so great that I'd been concerned that things wouldn't work out. Everything is just fine, now.
Apple had wanted $500 for two gigs (instead of 512 megs). Crucial had wanted about $360 for two gigs (and I could keep my old 512 megs). I picked up two one-gig SO-DIMMs from Newegg, where it was only $166. That means I way paying about a third of Apple's price and ending up with potentially usable-later DIMMs. (Well, probably not.)
I think I will use the savings to... save! I might use a tiny bit of the $333 that I didn't spend to upgrade my OmniGraffle license, or to get a headset for my phone. The rest goes into The House Fund.
For anyone who wants to do what I did, I ordered Patriot PSD21G6672S. One of Newegg's reviews said it would not run at the advertised 667MHz, but the hardware profile shows otherwise.