matrix.itasoftware.com is your friend.

If you're actively looking for such things for miles, a strategy I've found useful is to use Travelocity Dream Maps or airport Web sites to find legacy spoke cities that have non-stop or one-stop competition from low-cost carriers.

For instance, Oakland to Burlington, VT is now served OAK-JFK-BTV on jetBlue... so US/HP and UA have slashed their fares on that city pair... with routing rules that allow three connections in each direction! Then it becomes a matter of piecing together the flights that have the right fare buckets, as chrisw mentioned.