Modular plug-in based Open Source SCADA system developed in C# for small to medium installations.
Source code available at SourceForge, http://rtscontrol.svn.sourceforge.net/viewvc/rtscontrol/ [1] 1
1 Please note this code is somewhat outdated; if there is enough interest work will be continued.
Links:
[1] http://rtscontrol.svn.sourceforge.net/viewvc/rtscontrol/