most of the midrange PIC uC have i2c hardware built in, look for a module called SSP or MSSP (synchronus serial port). However, I don't think that module exists in the 12 series, they're just too tiny ... so you will need to emulate the different timings and whatnot, with software.
I don't have any examples for you, but I'm sure there are some at microchip.com and certainly google.com
the 508 as I recall, is an 8 pin device, with 5 I/O and 1 Input-Only pin ... I'm not sure I'd "waste" 2 of my I/O lines with an i2c eeprom ...some of the newer 12F chips have eeprom built in, or perhaps consider 1-wire eeprom?