OSGeo-Live is a self-contained bootable DVD, USB thumb drive or Virtual Machine based on Xubuntu, that allows you to try a wide variety of open source geospatial software without installing anything. It is composed entirely of free software, allowing it to be freely distributed, duplicated and passed around.
It provides pre-configured applications for a range of geospatial use cases, including storage, publishing, viewing, analysis and manipulation of data. It also contains sample datasets and documentation.
To try out the applications, simply:
Many applications are also provided with installers for Apple OSX and Microsoft Windows.
A half hour presentation, highlighting all OSGeo-Live applications, is available as a video, along with source slides and script.
Details at http://live.osgeo.org/en/presentation.html.