Free Software - Document Readers:

Adobe Reader
You can open PDF files (a common Web file format) with this free viewer from Adobe.
Adobe Reader

Microsoft Word Viewer
You can open documents created in Microsoft Word with this free viewer. Update the viewer with the patch to open latest Word files.
Microsoft Word Viewer
Patch to update Word Viewer 2003 to 2007

Microsoft PowerPoint Viewer 2007
You can open documents created in Microsoft PowerPoint with this free viewer.
Microsoft PowerPoint Viewer 2007

Microsoft Excel Viewer
You can open documents created in Microsoft Excel with this free viewer.
Microsoft Excel Viewer

Free Software - Web Browsers:

Internet Explorer
Latest version of IE from Microsoft.
Internet Explorer - latest version

Firefox
A popular alternative to Internet Explorer.
Firefox
Firefox (Mac OS X and Linux versions)

Free Software - Media Player:

Winamp
A popular media player, will play audio file formats such as MP3, AAC, etc, plus video files.
Winamp