In addition to the obvious, I've been looking at some social media lately. Here's a few items that I think are interesting.
Mashups of blogs, forums, into one community. Check out the homeschool TV example blog post.
Weird graphical social media called Symbaloo about educational websites.
Tremendous opportunities to create homeschool blogs with wordpress on random domains.
There are plenty of forums about homeschooling some are distinctly Christian homeschool program (or Christian homeschool views), others are more about eclectic non-religious homeschooling.
Many Christian homeschoolers use Time4Learning because it provides an engaging effective education with interactive fun. Many Christian families have questions related to the worldview and philosophy of Time4Learning and how it fits into the education they are providing their children.
Here's an embedded Symbaloo Webmix on Education
Time4Learning has created an online forum for their high school students which has a Facebook-like feel to it. It's called Time4Friends and is heavily moderated by homeschool parents.