Although the 30 DC has passed, I have been going over all of the training and blog articles to refresh/catch-up on what I missed.

They bring up a great concept on clustering and building a network of websites to drive traffic to a major money making site. The idea is to form clusters around keywords that you want your main site to own. Create content sites around those keywords and have everything point back to your site. 

Day 21 - The Big Picture | Mike Mindel - Thirty Day Challenger