If you have a tool to share, please comment on the post with a link as well as a brief description of tool. If you can, also note if an account is needed, if a tool must be downloaded, and if the site requires teacher override, as that would be helpful.
These categories come from the great article Introduction to Inquiry Based Learning by Neil Stephenson (@neilstephenson).
Locate Current Information
Tinker with Ideas
Organize and Synthesize Concepts
Collaborate and Share with Others
Programming and Computational Thinking
Participate in Learning Communities
As well, here are the technologies we have available on school computers.