You've absolutely got the problem defined. There isn't a very good open source solution for truly CADing parts yet, yes, there are plenty of programs out there to generate 3D models, but none of them are focused around the engineering aspect of modeling a part. If you're interested you could take a look at:
But I'd like to use something closer to:
I've used NX and Solidworks extensively, I know there are student licenses floating around for AutoCAD. Fortunately (maybe) Solidworks is in town, I need to get a phone call out to them to see if they'd be interested in donating a few licenses so we can legitimately use their products. Down the road I could certainly see Sector67 investing in a license to one of these programs and providing it as a service available to members.
As far as getting code from CAD to gcode (CAM), there are lots more programs to choose from, many of which are free/cheap/open source. One of the great things is with the Makerbot/RepRap projects there is tons of interest in generating gcode, so we're fortunate to have:
I have experience using FeatureCam and MeshCAM, but we could certainly use the open source versions to avoid dealing with licensing/costs.
The mills have Anilam CNC retrofit kits and use belt driven DC servo motors, a 1100M and a 3300M controller. The 1100M works great (currently running), the 3300 isn't turning on which hopefully turns out to be something simple. We'll be using the 1100M as a full 3 axis (when necessary, 2 axes cover about 90% of runs) and the machine with the 3300 will be used as a manual mill with the CNC system serving as an expensive digital readout (once it's working. . .) since the mill still has an intact quill feed.
If you're interested in learning/helping getting the machines running you're more than welcome to lend a hand (anyone else?), I don't have any experience with these particular CNC controllers but one of the people from the shop they came from has volunteered to stop out when we have them assembled and answer any questions about them. The good thing is the interface with all of these systems is relatively unsophisticated and Gcode is pretty straightforward (/have played with CNC equipment for 4 years) so we won't have any major things to learn, but I can guarantee hiccups and bugs as we define a toolchain to get from model to part in hand.