I've been getting ideas for cases, but I don't have anything to model with. I don't have a 3D printer, but someone I know works at a place who can use CNC machines to make whatever I need. Any good recommendations?
+1 for fusion 360. I love that I can go back and undo a specific change without undoing the changes I made since then. It also has some super useful tools, like hollowing out a shape to make it a shell.
Fusion 360 is awesome to use!
I highly recommend this video, as it introduces most of the important tools/methods that you'll need for modeling your portable.
Fusion360 is the best for hobbyist today. It is free and has revision history. It has a lot features that required very expensive software until recently. Particularly the analysis and CAM. Supposedly it can integrate with one of the circuit design programs but I've never tried it.
Setchup was a nice free stop gap until a good free modeling program was available but it wasn't great at anything besides pretty pictures. Being able to create a contoured terrain from satellite info was cool but they effectively killed that feature.
AutoCad was the old standard for 3d modeling but it is more of a drafting program. It still is the most widely used 2d drafting program
MicroStation is similar to AutoCAD but used more in the civil world such as bridges and railways
Solidworks and inventor are the main players in machine design.
Revit is the biggest name for building design
Most of these you can find a way to get a "free" or "education" version of but the locked features ruin the functionality of most of them.