What are some good older devices that I can scrounge i2c or spi modules from?
After several years scavenging parts, I can tell you that it is difficult to find I2C or SPI through-hole chips... But, many of the devices by themselves have these communication protocols somewhat hidden. One example is the Wii Nunchuk (I2C), SD cards (SPI), some multimeters (SCI)...

My recommendation: start with some of those and then buy a simple soldering iron to scavenge SMD parts, or sample/buy. You will realize that the price of the component ($0.6?) is NOTHING compared to the time you will spend trying to make it work :D