With no prior warning, Twitter has changed how apps can access images sent through Twitter's Direct Message API. Twitter was unable to give prior notice for security purposes, but the changes are in effect. Twitter encourages developers who access images through the API to check their integration.
A project of the Elgg Foundation, Elgg is a free open source social networking engine licensed to users under the GNU Public License v2. The REST Elgg API allows developers to integrate Elgg and offer new apps for it. To give a sense of its size, 1,646 plugins have been created so far by the user community, with nearly 3 million downloads. Examples of plugins include blogs, forums, social bookmarks.
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.