Orange is an open source data visualization tool, it seems to be quite nifty, however it is a bit tricky to get it to run under Ubuntu 10.10 (or any other Ubuntu if you've got Python 2.6 installed).
There is a very short guide on how to add the repositories and install Orange using the Debian package management tool that Ubuntu uses. The guide does however only cover how to get the actual files on your computer on not how to get Orange to actually run.
The main problem lies in the fact that Orange assumes your Python install to be 2.5, even though it will run on newer versions.
In the Orange forums there are some posts on how to get Orange running under different versions of Ubuntu, the different fixes mentioned there did however not work for me, but with the help of this post I was able to get it to run. The only thing needed was to change the content of /usr/bin/orange to
exec -a "$0" /usr/bin/python /usr/lib/python2.5/site-packages/orange/OrangeCanvas/orngCanvas.pyw "$@"
This simply makes sure your Orange installation knows where your Python installation resides, in order for Python to know where your Orange installation resides the first of the two lines above should be added to your .bashrc.