Depending on budget you can get cheap delta peak chargers for 5-7 cell nimh for around 15.00 us (plus shipping)
http://www.amondotech.com/index.asp?...S&Category=238

Personally I think if you have the money you should get a better charger that will handle 4-8 cells so you can charge your transmitter packs as well ($35) or lipos so that if you decide to get lipo packs you don't have to upgrade your charger as well this will run you around 100.00 ( I use a MRC Super Brain 977 with maxamp 4400 NMiH packs in my tanks and I run 2100mah NMiH packs in my radios)