Expion, a Social Media Management System (SMMS) company, specializes in helping companies manage their brand images on social networks, from Facebook to Youtube to Twitter, often relying on partners' APIs to pull of some of their more interesting feats. Most recently, it was chosen by Google as a Google Plus API partner for the brand-focused Pages feature.
There have been a lot of new socially based mashups showing up recently. In fact, we recently topped 700 social mashups. While many of these use the Facebook API or Twitter API, there are many more social APIs. The mashups below run the gamut, though, yes, also include Facebook.