Did you know OneBusAway is on twitter? Check us out at at http://explore.twitter.com/onebusaway.
They say that Twitter is what you make it, so we've mostly been using it in a customer service fashion. Specifically, we keep tabs on mentions of OneBusAway on Twitter and try to respond when people are having problems. We also occasionally post service notices when things are down or wonky and it's not worthy of a full blog post.
In the future, we'd like to add services notifications about temporary route changes and other issues using Twitter. Either way, we're just as new to Twitter as anyone else, so it'll be interesting to see how it all evolves.