I think Bigwig has become my favourite bit of code that I’ve ever worked on.
Before Bigwig, it was Object Factory, before that it was a Delphi class that I used to create tree-structured data (imaginatively called TNode).
Bigwig’s doesn’t have a test suite and it’s not even my code – it was [...]

I’ve just done a quick post at the Brightbox blog detailing their use of free and open source software and showing some of the free Brightbox projects.
In particular, Warren & Bigwig and Object Factory could be of use to many people and are probably worth a look.