I know that mileage runs are part of a sub-culture that not many people participate in, however, EVERYONE wants a deal (especially alerts to mistake deals). So the sites that I follow are good to scour for good deals in general. I wanted to share my go-to list:
Twitter: @TheFlightDeal; @SecretFlying; @FTMileageRuns. I set alerts to roll though but have the sound off. I then manually set the order of my alerts on my phone so things Twitter alerts are grouped together.
I have a premium subscription to Scott's Cheap Flights (it is a very inexpensive cost).
I also find things the old fashioned way: hunt on my own. I typically use ITA Matrix or Google Flights. I just punch in destinations and length of stay/time periods.
What sites do you use?