I created a resource blog just before I started teaching on italki: http://www.enupgrade.com/
There are many resource sites out there, but I intended to create something that tied neatly into italki and the lessons I offer as a teacher. To some extent it has been successful in drawing more attention to my teacher profile and bringing some lesson requests.
After seeing a site called English Bee that a group of English teachers have developed, I began to wonder about how best to fill gaps in resources for all areas of language learning. True collaboration is difficult to achieve, but I would like to put this out there in case any other teachers might be interested in contributing ideas and resources (with due recognition).
You can send me a message if you are interested.