Believe it or not, there is such a thing, that is, an ADC to VGA adapter. I bought one from MacConnection because I was not originally planning to buy any new monitors at all, but my 17" Studio Display CRT died two weeks ago, and then I went on a spending binge. Unfortunately, the only thing purged was my bank account.
I purchased both the DVI to VGA and ADC to VGA planning to hook up my old monitors to the new beast. Now I don't need either one of them, but had to get an ADC to DVI adapter. I've spent $100 just on display adapters. That's sick.
[edit] I lied. I bought from the Apple Store online, but it's a Belkin product and I had to do a search on "ADC to VGA" to find it. If it was listed on the 3rd-party products page, then I missed it.