I've been teaching myself some liquid state theory for a coarse-graining problem I am interested in.

- The classic "Theory of Simple Liquids" by Hansen and McDonald is of course a great textbook.
- Another freely available introduction, especially focused on the Ornstein-Zernike equation and its closures, is this readable chapter by Nagele called "Theories of Fluid Microstructure" (pdf). This presentation, which closely follows the material in the chapter, is also useful as a review.
- Finally, I found a very nice description of the equation, closures, review of numerical techniques to solve the OZ equation, and (wait I am not done) - python program - called pyOZ - to solve the OZ equations. While it is no longer actively maintained (last release was 2009), it is a very handy resource. Thank you Lubos Vrbka!
- There is also a Fortran 90 OZ equation solver that is maintained as part of a larger project here.
- Per Linse has a better documented OZ Fortran 95 software.
- A reasonably straightforward explanation of the computational method used is described here.