SageModeler is a free interactive graphic design tool students can use to diagram the structure of a system, runs simulations and much more.

Use the drag-and-drop features to also create static equilibrium or time-based dynamic models.  Students can add data to run simulations without having to write code or mathematical formulas.

This tool is being developed by the Concord Consortium at Michigan State University, specifically for middle and high school students.  It includes curriculum units and a teachers guide.

TeachersPayTeachers has a huge selection of 2000 free printable graphic organizers  for writing, reading, history, and science for all grade levels.  Excellent navigation tools help teachers and homeschooling parents drill down to the type of organizer you need.  You’ll also find lesson plans and other kinds of printables on the site.  All material are created by teachers.  You may submit your own orginal work to the site for purchase or to share freely.

WiseMapping is a free interactive graphic organizer, a mind mapping or concept mapping tool. The toolbar along the top makes it easy to organize ideas and regroup them according to your needs. Change colors, add links, notes, and icons to your nodes. You can publish and share your completed mind map, post it on your website, etc.

Freeology offers about 100 downloadable PDF-formatted printable graphic organizers for a wide variety of uses. They include reading and writing organizers, KWL, venn diagrams, concept mapping, and Cornell notes. There are also several poetry writing tools.

This collection printable graphic organizers is useful for reading comprehension, concept analysis, and for planning writing across subject areas. For all subjects, there are organizers for cause and effect, comparison and contrast, chain of events, cycle of events, hierarchy, and more. For literary arts, there are organizers for character analysis, story structure, and development.