There's also quite a lot of rather interesting and scrapeable data coming out of the usage patterns and conveniently supplied by TFL...
and a cool Earth visualisation:
Missing TFL Apps I would (probably) pay (a pound) for:
1. Bus Tracker App with live GPS updates from buses.
2. Bus App that let's you use your Oyster card RFID signature to tie 'rate-this-driver' votes to the bus you are sitting on at that time.
3. Tube App. You know, with a journeyplanner and an alternative routes planner and a 'body-on-the-tracks-at-Vauxhall' alert and a 'northern-line-normal-service' alert.