I only did for about ten minutes looking at ESL specific area. I have come to this site before for writing resume for more advanced students. That was more general area. It was really obvious from the beginning this was a good resource.
ESL handouts materials are the ones that we should all have, but don't always have access to. In my school, schools supply textbooks and they don't have too much reference materials in that particular book. The school can't afford to buy better books with more meat. Ironic, but reality. So this is collection of handouts is immensely valuable.
Materials seem to be picked according to the needs of ESL classes. ABE (Adult and Basic Education) programs normally are run with slim budget, any teacher and any program can have more suppliment materials. I try to organize a class by theme and when the need arises for grammar or specific points in details, the materials presented here work really well.