My own little visualisation of Tube trains. Currently serving lines with no splits (the line-drawing code can't quite do those yet) - others are on the way.
Much thanks is owed to traintimes.org.uk/map/tube.
Note that this uses canvas and font embedding. IE definitely won't work, others should.
Source is available on BitBucket, and my personal site is also worth a look, even if it's not got moving trains.