I have an obvious bias in favor the resources offered by The New York Times Learning Network since I write a monthly column for them on teaching English Language Learners (look for my new one this Thursday on teaching about the Presidential election). However, years before I began writing for them, they were number one on my
The Best Places To Find Free (And Good) Lesson Plans On The Internet.

Today, they published a short video on how to access their resources. Also, you might want to consider reading 12 Ways to Use The Learning Network Blog This School Year.