EPA leapt into the social media world in July 2007 with our first blog post. Ever since, we've been working to expand our options. That's been greatly helped by the terms of service that GSA has negotiated on behalf of all federal agencies (most agreements contain clauses we can't accept as federal agencies for various legal reasons). See howto.gov for the overarching process and the list of sites for which they've negotiated federal-friendly terms. Even when GSA finishes, each agency still needs to review the agreements with its own attorneys, but our internal review usually goes pretty quickly.
I find it helpful to know what others are doing, so in that spirit, here's what we're up to. You can find most of our accounts linked from our social media page. The links below go to the home pages of the various sites so you can check them out.
First, we've recently finalized agreements with several new services:
Meanwhile, here's what we're currently using. How much we're using each varies, from a lot (Facebook, Twitter, YouTube, Google+, and Flickr), to very little (Dipity, Cooliris).
And here are the sites with whom we've signed terms of service agreements, but aren't yet using. Reasons why not vary, from not yet finding a good project (remember, identifying the mission need is always the first step) to there being other legal or logistics issues we haven't yet resolved (or even tried to resolve).
What other social media tools/channels/sites are you using or thinking about?