We use serial EEPROMs in several applications. Used to store phone numbers, user profiles, timer settings, etc. The advantage of serial EEPROMs for us is board space. You can get an 8Kx8 device in an 8-pin package.

Jay:
Interesting comment on writing 00's to unused internal CPU program memory. I read through the program lock bits in my data sheets, and they are somewhat ambiguous (now there's a shock - a data sheet that isn't crystal clear) about being able to read ROM when set. The OTP data sheet I have (Intel 87C51Fx) says setting the lock bits disables further programming. The FLASH data sheet (Atmel 89C52) also states that further programming is disabled. If you have to erase it to reprogram it, and you can't read what is in it before you erase it, how can you get around the lock bits? Am I missing something?