What are the best examples of arts organizations using social media?

Looking for examples around audience engagement, audience appreciation, ticket sales, advocacy, and customer support:

Facebook.com/WeMergeMagazine is starting to do a lot more local events in South Florida collaborating with non-profits. :)

On The Boards - They are a performance space in Seattle, Washington focusing on more experimental performance-based work. They have been using social media for years, include a blog, Myspace, Facebook and their recently launched OnTheBoards.TV

Brooklyn Museum has done great work with the FirstFans program using Twitter, Foursquare, and other tools.

Theatre Communications Group (@TCG / http://www.facebook.com/tcg.org?ref=ts) is doing excellent work within the theatre community and communicating to arts advocates outside the industry.

The 2am Theatre website -- http://www.2amtheatre.com -- began over on Twitter as a conversation among theatre folk one night. The site is a "gathering place for ideas" and "thinking outside the black box," highlighting ideas for all kinds of theatres from storefronts up to major regional theatres. Many of the ideas include new and best uses of social media, audience development, marketing strategies, building community among your patrons and even among your local theatre companies. Often, blog posts grow out of conversations on Twitter itself, searchable with the #2amt hashtag.

The Walters Art Museumin Baltimore. They have a truly fabulous Twitter feed as well as a blog written by their Executive Director that is hosted by another organization. On their museum's website they also have a vast amount of artwork digitally reproduced in high-definition photos with tons of information, and you can subscribe to RSS Feeds of their 'Artwork of the day' or their latest acquisitions: http://art.thewalters.org.