I used to have a website called "Gas Buddy" and gave it up to pursue other opportunities, but it looks like
GasBuddy.com has evolved to a very useful site for saving on gas. For example, I am using it for the drive to WPT Montreal:
585 km, $59 in gas, 5 hours & 36 minutes, "Carbon Footprint" of 291 lbs; best station to fill up is for 117.3ยข in Lancaster.