I made this sheet of signs and symbols when I was an explorationist at Statoil. I had always used Macs until then, and wrote my thesis in LaTeX; both make it very easy to write scientific signs and symbols. It seemed to be a struggle on the PCs we had at Statoil, so I made a cheatsheet of keyboard shortcuts for myself.
I sent it around to some people when I left ConocoPhillips and some said they liked it. So I thought I'd put it here for anyone to take. The idea is to print it out and put it on your wall. Next time you catch yourself writing 12 km2 or 25oC or not bothering with the pesky acute accent in resumé, just glance at the list. On Windows you would hold down the Alt key, then with NumLock on, type out the number indicated on the number pad (the numeric keys above the alphabet keys won't work).