I am impressed by the Sankey diagrams produced with ‘sankeypython’, a new open source project. I first came across this in a discussion forum, where Yannick Copin from France presented his work using matprotlib. The project is now at Sourceforge, and several Sankey Diagrams in Python samples can be seen there.
Sankey for Python sample 1
The most important functionality is available, such as labels for flows and units. Diagrams have a basic left-to-right orientation, with vertical arrows branching out on both sides. Color changes seem to be realized by combining several systems. There are apparently no node objects where the flows directly hook to (as is common in other tools), but by interlacing differently colored Sankey arrows a process step becomes kind of implicit.
Sankey for Python sample 5

This has only been up on Sourceforge since June 2011, so it will be interesting to follow further development on ‘Sankey Diagrams in Python’. I have added the project to the list of Sankey diagram software.

After the colorful Sankey diagrams in the last two posts, here is a black/white one to soothe your eyes…

Sample diagram left-to-right produced with DrawSankey matalb plugin. See http://leniwiki.epfl.ch/index.php/DrawSankey

It has a left-to-right orientation, with inputs from the left, and losses branching out to the top. Made with Matlab add-on m.DrawSankey from EPFL Lausannne.

Just came across a new piece of software for simple Sankey diagrams.
DrawSankey.m is a routine for Matlab that allows to produce diagrams like these:

Sample output of drawSankey.m plugin for Matlab from EPFL Lausanne.

DrawSankey.m is from the Industrial Energy Systems Laboratory (LENI) at Swiss EPFL in Lausanne. Find more information on their Wiki.

I haven’t tested it myself yet, but this definitely looks like an interesting add-on for Matlab users. I have added drawSankey.m to the Sankey software list.