Here's some opensource software that I have worked on.
https://github.com/demian0311/silobase
At work we wanted to give people within the company ad-hoc access to data. But we didn't want to give them complete access with a SQL tool and we also didn't have time to write custom reports through our entire software stack.
You specify data sources and queries in XML. The XML contains SQL queries with place holders, we parse the queries and wherever we find the place holder we create form elements so the user can specify values.
It's not much, kind of ugly but it worked well for the task. There isn't much code here. It highly leverages the capabilities of Spring JDBC template.
https://github.com/demian0311/pagin8
I installed WordPress on my anemic little SliceHost VPS, it didn't perform as well as I think it should. I looked at other static site generators like rizzo and octopress but for various reasons I didn't like what they had. I probably should have given them more of a chance, octopress in particular has a good community and plugin support. rizzo is implemented in groovy, that's the language I chose for Pagin8.
To create your site you just put HTML, CSS and markdown files in an input directory. You can define and use aliases, include other files (for headers and footers) and create blog posts in both HTML and markdown.
http://sourceforge.net/projects/pyborg/
This is a wiki system in Python CGI. You could define your own wiki syntax to some extent. It also had a hierarchical concept for wiki entries.
http://sourceforge.net/projects/pix/
Given a directory structure with pictures and some meta-data, the Python CGI script will render a site for viewing images. It also creates thumbnails of your images.