If you are in floating modelspace (i.e. inside a paperspace viewport), CTRL+R cycles through other viewports, making each active in turn. This is useful for activating a viewport that is completely contained inside another.
I've been sending these tips out to my office once a week for about three years now, and decided to start the blog as a way to put them all in one place. Who knows, maybe they'll help somebody else out there too!
Some of the tips are pretty basic, but hey, we all had to start somewhere.
Most of the tips apply to AutoCAD 2004 & up -- I'll try to note if it's only available in later versions, but no promises. And ALL the tips apply to AutoCAD LT.
As always, if you have a tip you'd like to see featured, send it on in!