Hi Arif,
Check out the PIC 16F628 It has the following features. Combine that with the 8 pin 12C508 and you got a dynamite processor.
2K program memory (instead of 1K)
224 x 8 Data RAM
128 x 8 EEPROM data memory
15 I/O-pins (instead of 13)
Internal or external oscillator (instead of external only)
Capture, Compare, PWM (CCP) Module
Hardware USART
Analog comparator module
Now. Imagine paying $3.25 less for this microcontroller than the PIC16F84, and you have the PIC16F628. Not a bad deal, and they're simple to use.
The following web pages have some useful information.
http://www.rentron.com/PIC16F628.htm
http://www.rgp.nl/pic/adapter.htm
Regards,
Charles Bannister