This is just a small sample of available free tools.

Mozilla Firefox (browser):  http://www.mozilla.com/en-US/firefox/personal.html

Mozilla also offers a large and growing number of add-ons to the browser, to increase its functionality and enable everything from video downloads (Video Download Helper) to aid in compiling bibliographic data for research papers (Zotero):

https://addons.mozilla.org/en-US/firefox/

cnet:   http://download.cnet.com/windows/     

Thousands of free downloads - search on topic.  Free, demo, and shareware editions of many different types of software.

Jing:  http://www.jingproject.com/

Easy, easy way to capture screen shots and record short videos of your screen to share with other people.

Audacity:  http://audacity.sourceforge.net/

Audio recorder, easy to use basic functions, with some sophisticated editing and mixing capabilities.  Good for podcasts, narrated  PowerPoint slide shows, music tracks to accompany videos.

Open Office:  http://www.openoffice.org/

Free software to create documents, spreadsheets, and presentations that are compatible (mostly) with Microsoft Office.

Gimp: http://www.gimp.org/

Free picture and image editing software.

Skype:  http://www.skype.com/intl/en-us/home

Free voice and video calls to other Skype users.

Microsoft DreamSpark:  https://www.dreamspark.com/default.aspx

Microsoft offers free copies of software such as Visual Basic, Visual C++, Windows Server, and much more to high school students.  Need to register your school for students to obtain the software.

Geogebra:  http://www.geogebra.org/cms/

GeoGebra is free and multi-platform dynamic mathematics software for all levels of education that joins geometry, algebra, tables, graphing, statistics and calculus in one easy-to-use package.

Tux4Kids: http://tux4kids.alioth.debian.org/index.php

This organization has developed math, typing, and drawing programs for kids.  All are free to download and are multi-platform.

Google SketchUp:  http://sketchup.google.com/intl/en/

This is a free 3D drawing program.  Very easy to use and can integrate with Google maps.

Lego Digital Designer: http://ldd.lego.com/

Not sure of the educational value of this free program, but if you can find one it will surely keep boys interested.  This program lets you build with digital Lego blocks.

Google Earth - http://earth.google.com/

Free download with amazing capabilities of exploring planet Earth.  

See also Google Mars - http://www.google.com/mars/

Microsoft Photo Story 3 for Windows: http://www.microsoft.com/windowsxp/using/digitalphotography/photostory/default.mspx       

Create a web page of photos (Windows only).

iPhoto - http://www.apple.com/ilife/iphoto/    

Photo manager for Macs.

Educational Discounts

Academic Superstore:  http://www.academicsuperstore.com/

NOT FREE, but cheaper hardware and software!  One of several sources for students and educators to obtain software with discount pricing.  Most vendors who offer academic discounts require some form of verification, and they also offer the software on their own websites.