"Open source educational software is rapidly gaining adoption in a wide array of teaching environments." List of open source apps by function and what apps they replace.
A very potent, multi-media organizational tool for constructing arguments - based on Clarkson's box. Easy to use but somewhat abstract for younger users.
offers an extensive list of shared VFT's, and a template for creating your first VFT. The first is free, and can be published to their list. After that, a small annual fee.