This site has a large number of TechPosters and Cheat Sheets for the IT guy. While the page linked has some of the really good Linux Posters and Cheat Sheets including:
Anatomy of a Linux system
The Unicode Character Code Charts By Script
Vi Cheat Sheet
VIM Quick Reference Card
Vi Quick Reference
Vi Reference Card
Adobe Flex Framework 3 Classes
GNU Calc Reference Card
XEmacs Reference Card
Unix commands reference card
be sure to check out the right column to find others including HTML that can be very useful. Nice to have many of these in one place. Link it on Delicious.