Greg,
I think building your own charger is a great idea. Audioguru is right about Maxim too, they have some IC's that are really tailored right to what you want to do. Are you charging individual AA or AAA cells, or the sub-C RC packs??
It looks like Maxim has some new chips out for those single cells the DS2714 looks like a really good one for like those single cells. I was looking into the MAX712 and MAX713 for my RC packs. Just search on the Maxim site for these part numbers and they will even give you schematics as well to try out. Just a little word of caution, which you probably already know, it does not take much for the NiMH cells to start to vent. So I would be very conservative on your charge currents, and don't charge at really high currents.
Hopefully this helps out a little.