TfL launched a new cycle hire scheme, but didn't provide an API for the availability data. They did provide a map of all the docking stations, though, which has the availability data embedded within it.
Tom Taylor scraped that data and drew graphs of availability over time. TfL's load balancing system - perhaps - seems to be making the availability numbers fluctuate in weird ways.
Ed Everett made Dockr, which is like my app but better.
There's at least one decent iPhone app that shows nearby docking stations on a map.
Oliver O'Brien made a very nice visualisation of cycle availability across the whole city.
There's still no official data feed from TfL.