I found two very useful sites, based upon collaboration between teachers:
http://iteslj.org/questions/
http://a4esl.org/
There are other links there, just have a look. I hope they are helpful for those that are looking for materials.
two useful sites
Moderators: Dimitris, maneki neko2, Lorikeet, Enrico Palazzo, superpeach, cecil2, Mr. Kalgukshi2