I was wondering if anyone had any tips for good software (free is better) that I could use to produce .psp files which I could hand to a local laser cutter.  I just want to do this for myself, not make kits for sale.  I am very bad at cutting out parts for scratch building, but have had good luck assembling laser kits... so I would like to make some of my own design.

Anyone else already doing this?  What are you using?  What tips can you offer?

-SeanM