ReadWriteThink is a joint project of the International Reading Association and the National Council of Teachers of English. There are about 800 lesson plans here.
The New York City English Language Arts Performance Standards include about 75 lesson plans for elementary, middle, and high school.
The New York Times Learning Network site has a variety of lesson plans, submitted by readers who are also teachers.
TeAchnology: The Online Teacher Resource is a for-profit company that offers many free lesson plans on its site.