GeoGebra is a mathematics and science software used for learning and teaching. It is a free download that covers geometry, algebra, tables, graphing, statistics, and calculus. This software also has an authoring tool that allows creation of interactive learning materials that can be used as web pages.
Scriblink is a free digital whiteboard that users can share online and in real-time. Scriblink is a great collaboration tool. Scriblink could be used for layout planning, concept diagramming, and even tutoring. Features of Scriblink includes: privacy, dynamic tools, file options, image uploader, on-screen chats, voip conferencing, and file transfer.
ThingLink for Education
ThingLink for Education is a safe and efficient online classroom environment. It has a free sign up section for teachers and students. This website help teachers create interactive images to help students develop 21st century skills. The image interaction tools includes tagging tools also. The tagging tools gives photos a new life with music, videos, web, and other fun links.
ThingLink allows you to create image collages and add tags that give background information to the images and also to annotate charts and illustrations. After exploring this site I believe that this could be a very helpful 21st century learning tool.