Synopsys lens design program
 

It's free and almost fully functional for 90 days (limits to 12 elements). It's REALLY interesting: http://home.gwi.net/OSD/ It's a thousand dollars to buy, so good thing there's a free trial.

The image on that page is an example of what it can do... but the learning curve seems a bit steep. If you have red/blue glasses, you can even see a 3d wirefram of a lens system.

Just thought I'd put it on here, I'm not sure how many people knew about it.

interesting, im checking it out