Data collected: No data yet
The TfL API has temporarily been suspended, hope it's back soon (I only made 10 requests every 2 minutes, so don't think I was responsible for the 10m hits!). In the meantime, you can see a video of the site in action courtesy of Gary Gale.
This map shows all trains (yellow pins) on the London Underground network in approximately real time (screenshot). Click the stations for a local map of that station. I have a (per-station) National Rail version, and a bookmarkable train times planner.
Live departure data is fetched from the TfL API, and then it does a bit of maths and magic. It’s surprisingly okay, given this was done in only a few hours at Science Hackday on 19/20th June 2010, and the many naming/location issues encountered, some unresolved. A small number of stations are misplaced or missing; occasional trains behave oddly; some H&C and Circle stations are missing in the TfL feed.
Matthew Somerville (with helpful hinderances from Frances Berriman and James Aylett). Station icon by Tim Diggins. Source code.