I participated in the GSoC 2011 for the SHOGUN machine learning toolbox (link). This was awesome! The program brings together students (like me) and open-source organisations. You are getting paid to work full-time on a project you choose. I could really use the money and learned lots of lots of cool things and met nice people.

My project was mentored by Soeren Sonnenburg and had the title “Built a flexible cross-validation framework into shogun”. Here is the abstract:
Nearly every learning machine has parameters which have to be determined manually. Shogun currently lacks a model selection framework. Therefore, the goal of this project is to extend shogun to make cross-validation possible. Different strategies, how training data is split up should be available and easy to exchange. Various model selection schemes are integrated (train,validation,test split, n-fold cross validation, leave one out cross validation, etc)

The proposal I wrote can be found here. My motivation for the project came from the fact that I actually used SHOGUN for my Bachelor thesis (link). I had to do model-selection by hand these days. A major portion of the programming work I did would not have been necessary if model selection already was a part of SHOGUN. Nowadays, quite some people use the stuff I wrote during the summer 2011.