i might be sheltered because i use asp so much, but i would just make a simple asp script that saves whatever the user types into a custom database organized by the specific locations that you are entering for. then the specific location links for the website would just search the base and either report the last input, or say its not found.
if you were wondering, there is already a website that does what I assume you are looking to:
http://www.gasbuddy.com
I think a forum would get way to complex.
