Blender
http://www.blender.org/cms/Home.2.0.html
Blender is the open source software for 3D modeling, animation, rendering, post-production, interactive creation and playback. Available for all major operating systems.

Celestia
http://www.shatters.net/celestia
Celstia is a free real-time space simulation that lets you visually experience our universe in three dimensions. A special web site (http://www.celestiamotherlode.net) maintains libraries of plug-ins to enhance Celestia. In addition to free exploration, students can use scripts (http://www.celestiamotherlode.net/catalog/scripts.php) that provide journeys designed by educators to focus on certain aspects of space exploration.

Dia
http://www.gnome.org/projects/dia/
Dia is inspired by the commercial Windows program 'Visio', though more geared towards informal diagrams for casual use. It can be used to draw many different kinds of diagrams.

Educational Freeware
http://www.educational-freeware.com/default.aspx
This site is dedicated to listings, descriptions and reviews of the best free educational software for kids and adults.

Freeware for Kids
http://www.linkup-parents.com/freeware.htm
Free educational software for toddlers to high school students, this site has a good selection of freeware and shareware.

Freeware By Age
http://www.kidsdomain.com/down/pc/_agefreeware-index.html
Freeware is sorted by age on this website.

Freeware Home
http://www.freewarehome.com/
An indexed collection of FREE programs commonly found on the Internet around the globe.

Inkscape
http://www.inkscape.org/
Inkscape is an Open Source vector graphics editor, with capabilities similar to Illustrator, Freehand, and CorelDraw. Inkscape's main goal is to create a powerful and convenient drawing tool fully compliant with XML, SVG, and CSS standards.

K12 Open Source News for Schools
http://k12os.org/
K12OS.org focuses on Open Source news in education. You'll find news, links, resources and discussion here to help promote the use of Open Source software in K-12 schools.

Macintosh Freeware
http://www.pcsoftland.com/education/k-12/indexrating.htm
This site lists Macintosh freeware for middle school mathematics.

Making Decisions about Open Source Software
http://www.netc.org/openoptions/
Open source software may be a good solution for your state, district, or school. This site will help you weigh that choice.

Open Source Resource Links
http://www.k12opentech.org/index.php?option=com_weblinks&Itemid=23
This site provides links to several different types of free software.

Open Source Victoria
http://www.osv.org.au/
This site provides an excellent overview of Open Source software in education.

SchoolForge
http://www.schoolforge.net/
The software resource link on this page has a listing of great sites. Check out the the SEUL collection link.

SourceForge
http://sourceforge.net/
This site is a centralized location for Open Source projects.

The Best K-12 Freeware
http://www.education-world.com/a_tech/tech/tech208.shtml
This site provides a technology article on free software

UNESCO Free Software Portal
http://www.unesco.org/cgi-bin/webworld/portal_freesoftware/cgi/page.cgi?d=1
The free software directory on this site has great resources.