Man, I don't get why Teachers stress so much on lesson plans.
I was a high school teacher for about a decade and after the first three years, it doesn't take long or difficult to have lesson plans available.
If you want ideas, the school district often has a crap load of them. And if you are teaching a standardized course (like Algebra or Geometry) you are essentially provided lesson plans for every day.
The website is an interesting idea, but it won't make a bunch of people millionaires. It will make 2 or 3 teachers millionaires, with most people who contributed probably losing money for the amount of time invested in creating these lesson plans.
Really, the school districts biggest waste of resources are their teachers. You could easily open source all the teachers lesson plans for the district, then you could freely pick and choose from anyone in your district.
Also, you could do away with those crazy expensive textbooks. Get every kid a $50 android tablet and get a team of teachers to come up with an open source version.
It would take them a few weeks over the summer if you are dealing with experienced teachers.
Then, you update the textbook every summer and the students download the latest version in August.
The school district would save insane amounts of money.
But, they won't do that because the publishers and administrators have corrupted the textbook buying process to a maddening degree. So sad.