Great idea. I had a similar idea not that long ago, but did not execute. To build a good system for teachers to find and review lesson plans and teaching techniques. To build a productive social networking site for teachers to share experiences with other teachers.<p>The freemium model would work great here, if a few teachers gain a free foothold, and find the service useful, they can then go to their district and request to upgrade to the paid version for all to use.<p>Now it all comes down to execution.