The project Twitter account @s4s_oer was started to keep followers up to date with the latest developments in the project. This really took off when resources started to be made available as OER.
As each OER was uploaded to JorumOpen (or another repository/site) a message was sent out on Twitter including a direct link. The link was shortented using bit.ly which enabled us to see (through the bit.ly website) how many hits we were getting as a result of that message, and also any repeats of the message (a 'retweet' or 'RT') on Twitter sent by other Twitter users. We could clearly see spikes in visitor numbers following any mention on Twitter.
Although the project Twitter account has a very modest number of followers, using the programme tag ukoer brings our messages on Twitter to the attention of anyone following the progress of the programme, a considerably larger number of people. We've been fortunate enough to have our messages about new OER picked up and rebroadcast by others with a larger number of followers and so enabled us to reach a much larger audience.
An account of our use of Twitter can be found in this month's Jorum Update: http://www.jorum.ac.uk/docs/pdf/JorumMarchupdate.pdf