Rainbow:
http://www.rainbowportal.net/
http://sourceforge.net/projects/rainbowportal
Data Access Application Block:
http://www.gotdotnet.com/workspaces
DotNetNuke:
http://sourceforge.net/projects/dnn/
Iris:
http://marshine.nease.net/myprjs/iris
FCKeditor:
http://www.fckeditor.net
log4net
http://logging.apache.org/log4net
Spring Framework .NET
http://sourceforge.net/projects/springnet/
http://www.springframework.net/