I've been using this whenever I need gas for the last year or so.
http://www.gasbuddy.com
http://www.bostongasprices.com/
I don't drive far out of my way just to get cheap gas, but stuff that's in vicinity of home or where I am going for an errand, and depending on other variables like how ghetto a station might be in terms of brand or quality, I'll bite. Basically works great, use at your own discretion!