Right now I'm learning Blender for 3D modeling work. Previously I used Rhino, SolidWorks, and Autodesk Inventor. Switching to Blender because a) people here use it, b) it's free, c) it works across platforms and d) it seems to be just as powerful as the non-free, Windows-only modeling software.
Major shoutout to the awesome Wikibook that's making the transition easier: Blender 3D: Noob to Pro. Highly recommend.
Same author, Grace. This is where I make technical notes, usually related to my PhD. My slightly more exciting blog, Grace Under Pressure, is here.