The Ooyala SDK by Ooyala in C# interacts with the API to make calls and receive responses. Functionalities of the API include analytics, monetization, and content publishing features. Authored by Pepe Gasca. Additional documentation resources available at http://support.ooyala.com/developers/documentation/concepts/api_sdks.html
Just a quick pointer to a fun writeup by Jenny Shank about her husband Julien's experiences of creating and publicizing the very good mashup WeatherMole. The second segment of the story is a great account of the cycle of publicity that many mashups hope for.
If you wonder which of the 267 APIs on this site people view most often you might be surprised. It's not Google Maps, it's YouTube. Which has been true for quite some time. But the number of mashups using YouTube has been small, until recently when they've started to pick-up.
Snapchat recently opened up its long-awaited API to creative agencies and ad tech companies. Top players in the ad industry are already jumping on the bandwagon and these early birds are getting plenty of attention, writes Lauren Johnson over at Adweek.