"The Mayor of London Boris Johnson today (7 January) fired the starting
gun on an information revolution in the capital as he announced that
City Hall is to release online, for the first time, huge realms of
previously unavailable data for everyone to see and use free of charge. " see full press release [1]
http://data.london.gov.uk/ [2]
PracticalWeb has been working on this project under contract to the GLA since the beginning of December, it's been a satisfying month of activity.
The site is a fairly straightforward Drupal build with a couple of custom content types, and a theme adapted from one the GLA is already working on.
I've seen real commitment to opening up data and while the emphasis so far has been on getting the functionality right - I understand that more data will be released as quickly as possible in a range of open formats.
The site has RSS feeds so subscribe if you want to keep updated.