SU2: Open-source CFD Software from Stanford's Aerospace Dept.

From the Stanford University website:

At a recent demonstration, the Stanford team debuted "Stanford University Unstructured" (SU2), an open-source application that models the effects of fluids moving over aerodynamic surfaces such as fuselages, hulls, propellers, rotors, wings, rockets and re-entry vehicles.

Dubbed SU2 for short, the application incorporates everything engineers need to perform a complete design loop for optimizing the shapes of aerospace systems.  While commercial programs offering similar capabilities are available, they can be prohibitively expensive. SU2, on the other hand,  can be downloaded for free from the lab's website.

Source: http://engineering.stanford.edu/news/stanford-aero-engineers-debut-open-source-fluid-dynamics-design-application

Update: Version 1.1 of SU2 is available as of 06/29/12

Download via: http://su2.stanford.edu/news/news_release1p1.html

Many thanks to @FlightTestFact for the link!