My current favourite drawing package is tikz/pgf. This is an excellent package for drawing in LaTeX, you can include any equations you like in figures and exactly control where to put things.
About the Author...
Thomas is a meat popsicle. Thomas started working with UNIX while at SFU and UBC in Vancouver. Starting out on IRIX, HPUX and Solaris, he quickly transitioned to Linux in the early 90s. He has been a System Administrator and a Developer working mainly in Python and C. He's written several technology books, many dealing with Puppet and Configuration Management.