From super-effective search tricks to Google tools specifically for education to tricks and tips for using Gmail, Google Docs, and Google Calendar, these tricks will surely save you some precious time.
A great site with lots of resources for teaching reading. Yes, it is for L1 (US) teaching and learning, but this site has hundrds (!) of great lesson plans (including the actual reading text and teaching plan and worksheets) for fiction and non-fiction that could be used in any context where reading is taught. Registration required for downloading. The site also has great resources for learning how to teach reading more effectively.
Resources for the Communicate textbook series by David Paul are available online. Activity Bank resources and Activity Materials can be accessed here. There are some very nice ideas and activities by a well-respected teacher/author in Japan.
ClipPix ETC is your source for photos and pictures for classroom use. A friendly license allows teachers and students to use up to 25 free photos in a single, non-commercial school project without further permission.
Posters are great learning tools that we use in our classrooms. They attract students attention and they can seamlessly communicate various concepts and ideas . These posters feature classrooom rules and key grammatical structures, among other things. I'm not sure if they are all "must have" posters, but I think you may find some of them are useful.