Liz Azyan has updated her list of UK local councils on Twitter. On April 11th 2009 there were 101 with Newcastle City Council having the most followers (1050). She has also started lists of US, Canadian and Australian local government on Twitter.
Another useful listing from LizAzyan Research on what UK local councils are doing with respect to social media. As well as detailing which local councils are doing what on Facebook there is a nice table showing the difference between Facebook Fan Pages and Facebook Groups.
If Twitter is your preferred news medium and you want to keep up with what is happening locally, for example school closures due to bad weather, use Twitter / uklocalcouncils to track down your local council. A meagre twenty-two are currently listed and you can follow individual councils or all of them (uklocalcouncils). Content varies but usually includes news about jobs, changes to refuse and recycling collection dates, school closures and impact of severe weather conditions on local services.