Hi
take a look at the links i have pasted. they are great articles on how to use the ADC on small 8 pin pics.

http://www.rentron.com/four-channel-ad.htm
http://www.rentron.com/PIC12C67XAD.htm
http://www.rentron.com/PIC12C67X.htm
http://www.rentron.com/PICX2.htm

Micorhip makes the 12f675 which is the pic of choice if you want flash memory.

good luck

sam