Aside from the top platforms, Twitter, Facebook, Blogs, Linked-In, etc. what other Social Media platforms, or related do you like to use?

I am working on some documentation and I want to include some other platforms that I might not use well, or often. I would like to be able to share their function and use with others, so if there is one in particular, or more, I would love it if you would take a few minutes and post a comment and tell me the platform, the URL and why/how you use it.  And extra points for creativity!  So I can think of quickly – tumblr, flickr, buzz, and so on.

If you are in Real Estate this is obviously of special interest to me.

Thanks for sharing and helping!