When reviewing papers for a conference, someone referenced Z88 Aurora (http://www.z88.org) which is an Open Source, cross-platform (Linux, Windows, OSX) Finite Element Analysis software. It is quite extensive and comes with examples and documentation. There is also Z88 (without the Aurora) which is also Open Source. I'm not fully sure about the difference between both... but AFAIK, Aurora contains the more user-friendly GUI with more interactivity, whereas Z88 is more limited in scope.
It contains a pre-processor (load geometry and FEA files, meshing, materials), FE-solver (calculates displacements, stresses and node forces) and a post-processor (visualization of results, export to CSV).
For once, this software is (quite) easy to use on OSX as well, provided you have the X11 system installed, which usually comes with installing the Apple Developers packages, which are included with your OS system disk. It relies on a few external libraries, but even those are embedded or included as a separate download. I had little problem to launch it. But getting something calculated requires more effort ;)
There are even video tutorials included and the read-me PDFs are of quite good quality (even explaining how to configure your trackpad and magic mouse for Mac users).
|Screenshot borrowed from Z88 homepage|
I started manually defining the nodes (x,y,z), the elements/trusses (from/to node), add a material form the extensive included database, apply the different constraints (fixed nodes, forces) and then run the solver (which was finished before I even noticed something happening). The following screenshot shows onf of the results from the post-processor.