For those of you following the long OT comments discussion on graphics programs, let me second Chris’s endorsement of Tikz. It is by far the best LaTeX graphics package I have ever used. I couldn’t possibly compete with the manual (what other manual starts with 3 fantastic tutorials?), and this page of examples. I have a certain affection for xypic, which has served me well over the years, but Tikz is just lightyears ahead. That is all.