Thanks for the heads-up on mileagebrain. I was playing with it to see what kinds of results it came up with. I'm am not too far in, but I can tell you that it does not use any segment elite minimums. In other words, if you are an elite getting a 500 mile minimum per segment, the site will run it's math on the actual miles for the segment. I would think that most MR'ers are elites trying to maintain or improve status, so this makes a difference.
It could still be a valuable tool, just keep in mind that the cents/mile calculation will be off a bit.