Here is a periodic sampling from my del.icio.us favorites list. This time I chose the tag "Elgg." Elgg is an open source, and free-to-use social media platform that is often used for education, including the creation of personal learning environments.
Here is what I have:
Elgg: The site itself.
Elgg -- A Personal Learning Landscape: From The Electronic Journal for English as a Second Language, a thorough summary article describing Elgg, its elements, how to use it, how it compares to Moodle and other backgroung.
Using Elgg as as Social Learning platform: From the Centre for Learning and Performance Technologies, a how-to SlideShare presentation on Elgg.
Elgg, Ning and SocialText: From eLearning Weekly, a quick-and-dirty comparison of the three platforms.
SOCIAL LEARNING STRATEGY - Comparison of Facebook, Ning and Elgg: Again from Centre for Learning and Performance Technologies, a chart comparing Elgg to Ning and Facebook.