Connexions

Did you know about Connexions? From the home page:

Connexions is a rapidly growing collection of free scholarly materials and a powerful set of free software tools to help
* authors publish and collaborate
* instructors rapidly build and share custom courses
* learners explore the links among concepts, courses, and disciplines.

You should not expect that the courses and the modules to teach you all the details especially in the graduate level but it definetely serves perfectly when you need a quick reference or a summary of a topic either to get a quick start or to refresh your knowledge.

They also have a blog which is located under the Software heading. There is an RSS feed but I didn’t see any comment mechanism.