So you have a 3D printer (or drool after one :)) and have a lot of ideas for parts to make. What do you do? Learn a CAD program.
I have used Sketchup with great success. It is free and easy to learn, but have some quirks and bugs that are useful to know about.
Knowing how to design in a CAD program is only half the story. Knowing how to design around 3D printer limitations and know where to "push it" is also important.
If someone is interested and are able to provide a location with a projector I can do the "teaching" :) It could also be done "at home" without a projector, but it would be harder to do it as efficiently.
It could be done in the evening on weekdays or in the weekend. You could bring along your laptops and ideas for parts and hopefully we could print out the end results :)
If possible you should bring along a laptop with the latest version of Sketchup (www.sketchup.com) and the Sketchup STL plugin (https://github.com/SketchUp/sketchup-stl)