There are many sites that have open source circuit design tools. I will be listing a few I regularly visit. My interest is more in the area of software design, so access to the source code is what I am after. I use the code to learn about data structures, presentation, and various coding styles and practices.
http://opencircuitdesign.com/index.html
I am looking at Design Configuration Management systems at the moment. Currently DesignSync from Dassault Systemes is what I am concentrating on.
Synopsys Liberty Parser - The source is decent as a reference. However it is dead now...
Managing Perl CPAN modules under Fedora can be a challenge, so I have documented the procedure I use to wrap a Perl module into an RPM. I am also starting to experiment with the Shipwright and Carton packaging systems. The idea is to support creating custom distributions that can contain perl modules, and supporting libraries.