I bought an app for my Palm Pilot called TravelTracker, which is good for keeping track of flight/hotel/car details of trips, but is inadequate for tracking miles/points. For that I use a ridiculously large, complex Excel spreadsheet that I created for my own purposes and jollies. I have a feeling that most road warriors will agree that number of miles in the account tends to be less relevant than things like miles toward status, upgrades, etc.

What would be really nice is a utility that tracks both miles and hotel points, providing scenarios for how one might transfer points to miles and vice versa. That kind of thing makes my brain freeze.