Eighteen months ago Cool Tools introduced me to SketchUp (since acquired by Google). I love this tool but always missed the discontinued SpaceBall 3D controllers that I used with high-end 3D applications. We’ll, that’s changed. 3dconnexion (owned by Logitech) now sells a low-cost, very high quality, 3D controller called the SpaceNavigator. When I bought mine, you could get an edition for personal use that is only $59 (instead of $99 for the pro edition). This increases Sketchup productivity and fun factor by 2-3 times. If you like SketchUp you have to have this!
The SpaceNavigator is a six-axis controller that you use in conjunction with the mouse and keyboard. With it you can move around the model in three dimensions, intuitively and without changing from one mode to another (e.g. pan to rotate to zoom). You can also configure it to work in what ever fashion is easiest and most intuitive for you. With a little practice you can move through and around the model using the mouse and SpaceNavigator, never touching the keyboard. It provides a huge increase in productivity and, frankly, fun. I’m designing an addition to our house and my kids (6 & 8) have learned to fly through the model without my help. Of course you can use it with other 3D applications, like AutoCAD, Rhino and Maya.
This is one of those things that you purchase and fall in love with because it’s useful, high-quality, and inexpensive. (It works in Windows, Linux, Unix — but not Mac!)