hi, i suggest u to use the Atmel AT89S8252 which has got 8k Flash rom (Downloadable) and 2k E2prom in built. Programming the chip is really very easy. Look at the following site:
www.people.freenet.de/buss OR www.lancos.com

DS5000 is also a good choice which has got 32k NVRAM in built for program and/or data. But this is expensive and i couldn't get one.

mail me if any other help is required.
Thanks....