Let's talk about CAM

Norbert's advice is good. To start you really don't need a cam package. Better to start with a good 3-d drafting package, not a solid modeling package, and then get good with it. Use a free dxf to g-code converter and start making parts to get the machine dialed-in. Then look for a CAM package. I still suggest Meshcam. It looks simple and elementary but it's very powerful and very flexible and works well with Linuxcnc right out of the box.

I have checked out meshlabe for a little bit and it does seem to be pretty nice all around. Seems more capable than all but maybe heeks while being much more user friendly than heeks.

It seems odd to me that all these programs use meshes. Is it really that much cheaper or easier than using something like a STEP?

I am curious what you mean by 3-D drafting. I have a little experience with drafting programs like drftsight and librecad and know that they have some ability to sketch into the 3D but I have never looked into it much more than that.
If that is the type of 3D drafting you are talking about then I have zero interest in learning something that takes longer to make, longer to edit and gives you less control and functionality than what I already know and use.

Sounds like you already have a CAD and/or modeling package you want to keep so all you need now is some cheap and simple CAM package so you can add the tool paths and tool changes and then you're good to go. Just browse around and try out the demo's for various packages until you find one that you like and has a post processor for Linuxcnc.

Another one to trial (again Windows only, though) is www.deskproto.com

Take a look at SketchUp,( formaly Google Sketchup) it is free you can download a plugin call SketchUCam from phlatforum.com . It is also free and produces 2d as well as 3d gcode very well. I have tried to use google sketchup in Ubuntu it is possible but works better on windows.

This is now out of date check

www.forum.linuxcnc.org/forum/31-cad-cam/...t-cam?start=40#65406

I've got MeshCAM. Currently, it's the only available native Mac OS X CAM program. It has positives and negatives. Overall, I feel it's limiting. It tends to make mistakes randomly in the gcode. You really have to check it line by line. If you don't there can sometimes be erroneous gcode which will ruin your day. No ramp cutting. No rapid Z from your safe Z height to the surface of the work. So, the question about if this is a money making venture, or personal is quite important. Personal, then sure, MeshCAM is fine. You just have to plan to spend time hand editing and making separate programs to adjust for different areas which the program will omit. I also feel that the primary users of MC are wood router people, not folks cutting metal. If you're trying to make money, then spend the money now on the [insanely] expensive software. It will save you time and you typically can preview/simulate everything.