5 Ways Banks Are Using Social Media is a great post by Lon S. Cohen. He is @obilon on Twitter.
As a PR who works with banks I know the potential value of social media in that industry and the examples that Cohen features show that potential.
I am also a USAA customer. They are a credit union that have been using social media very, very well. They have also put in place amazing online features such as check deposit via an iPhone app!
Used correctly and with a specific purpose in mind, social media can be a tool that makes business more profitable.