You may be interested in this site http://teflplanit.com . It has been designed for teachers to share lessons, worksheets, reference articles, tests etc. You can create lessons, activities, articles, tests etc and share them, either with everyone, or just with groups you are a member of. You can create your own groups to share your resources with, for example, co-workers in your school.
There's also the option to include your own media ( images, audio, video ) if you are willing to subscribe. Subscription also enables users to copy and modify existing content to make it suitable for them.
It's still relatively new, so I'd be interested to hear people's thoughts and suggestions. I made it because while there is lots of material to be found through searching, it often wasn't quite what I needed. So I though if contributed content could be modified easily, it would be a good way of sharing material. It's taken a long time to make but hopefully it will be of some interest. I've made some material already so you can see what it's like. Register as a member and start sharing your great content!