Tangler, an online network of discussion forums, recently announced their new API. The Tangler service takes traditional discussion forums to a new level, by allowing anyone to easily set up a discussion forum that can grow to include hundreds of topics and thousands of users.
Socialmod is a system to either automate or simplify your site's social content moderation. Its socialmod API allows for direct integration of socialmod into your site, making using their service far easier. Its service has been used for such high-profile sites as the BET.com awards, as described in its blog.