Most places - like grocery stores - don't advertise what they have on tap on their websites. Do you guys just call the stores to see what they have on tap for a growler fill? Doesn't make much sense to drive out of your way when you don't have any idea what they are offering.
Dominion Wine and Beer in Falls Church, VA is now doing growler fills. They update their tap list via DigitalPour. You can see this at anytime through the DigitalPour app on their facebook page. Nothing mobile available yet unfortunately