Free Optics Simulation Programs
Goptical GNU-Optical
Description
Goptical is a C++ optical design and simulation library. Goptical is free software and is part of the GNU project.
It provides model classes for optical components, surfaces and materials. It enables building optical systems by creating and placing various optical components in a 3d space and simulates light propagation through the system. Classical optical design analysis tools can be used on optical systems.
It takes advantages of the C++ object model to allow building complex optical systems with a few classes instanciations as optical components are represented by language objects.
For record: It looks like this topic really interests some people: http://markmail.org/message/nic7xrgf5uzed5c4
Newport was obviously thinking in the same direction:
They offer an option to use SketchUp and provide 3D models of their mechanics and lenses—at least they used to, since this page does not exist anymore and the picture above was kindly sent to me by Newport to answer the request in the comment.
Having background in both optical engineering and experimental optics, I can say that real experiments and setups are usually designed with a piece of paper if they are simple or with the professional software if they are not. Real systems very quickly stop being a bunch of mirrors. This is, probably, why nobody is seriously considering creation of such a tool.
In labs, we are usually trying to align all beams parallel or under 90 degrees to each other---not only for ease of work but also because otherwise polarisation effects start being a problem.
There is also optgeo, quite simple, but could be useful in your case, you can drag and drop lenses, mirrors, beamsplitters etc. It is free software:
http://jeanmarie.biansan.free.fr/optgeo.html
It is also in the ubuntu and debian repositorys.