British Cycling and Sky have teamed up to put on loads of free bike rides around the UK - they have city rides and local rides starting out in London, Leicester, Manchester and Glasgow at the moment, with a view to getting more places involved in the future.
I think this is such a good idea, its as easy as registering on the website and just turning up with a bike on the day. Then you get to meet loads of people and effectively get a free guided bike tour. They only have rides up to the end of October at the moment, but I've bookmarked it for future reference as I think I'm definitely going to check some of these out at some point.
Go Skyride