I have just come across Piet Hut's and Jun Makino's Maya Project . The aim of this project is to develop software to perform detailed simulations of star clusters. Now I myself have quite an interest in star clusters and with my trusty copy of Numerical Recipes to hand I could probably work my way through most of the maths, but, to me, by far the most interesting thing about this project is the decision to document the development in the form of a dialogue between two astrophysicists. These dialogues cover the astrophysics, the maths and the software development and appear to contain a wealth of information and good advice on program development. The language chosen for the development is Ruby, which is an interesting decision in itself (and one which is discussed in the dialogues).
The development dialogues are included in the Development Series (use the link near the foot of the Maya Project home page).
One thing to note is that the project used to be called the Kali Project and there are quite a few references to this old name still in existence, in particular, the simulation system that is being developed is referred to as the Kali Code (researchers in stellar structure and evolution refer to computer programs as 'codes' - apparently a term left over from the very early days of computing).