I’ve just initiated a Google Code project with the extraordinary thrilling name odepy :-). This is a Python library for implementation, design and evaluation of numerical integrators for ordinary differential equations. I’ve used it for a long time in my research. The framework is designed in a way which makes it very easy to implement and try new methods. So far only explicit Runge-Kutta methods and arbitrary composition methods have been implemented in the framework, but I hope to soon finish implementation of implicit Runge-Kutta methods as well.