I still have a couple of the cheat sheets my study group compiled -- they're so fun to look back on. One for Computer Organization is almost unintelligible to me now; we were so proud of the density of that sucker.
did your instructor also allow a desktop microscope?
One of the more creative tricks I remember was writing a cheatsheet in red and blue text overlaid on each other and using 3D glasses to read it, which allowed you to squeeze more on. Never actually did it, so I don't know if it was useful...