When I went to set up my personal NationBuilder database (Wired to Share), one of the first things I did was go to my decade-old Yahoo! Mail account to export a CSV file of contacts to upload into NB. I hadn't pulled my Yahoo contacts in a long time, and was happily surprised by what I found.

Yahoo! Mail is fully integrated with Facebook, which means you can pull all of your Facebook friends' email addresses into Yahoo! and easily export them for use with other tools. This integration is more than a year old, but it was new to me. Yahoo! also imports from Gmail and a dozen other services. Grab your LinkedIn contacts as well and you're talking about a pretty robust email list if you've been using any of these networks for long.

Import these folks into NationBuilder as prospects and you can send them an e-mail about opting into updates from you.