Latex, with the TikZ package: http://www.texample.net/tikz/ http://www.texample.net/tikz/ Steep learning curve, but there are plenty of examples around the Int

Latex, with the TikZ package: http://www.texample.net/tikz/ http://www.texample.net/tikz/ Steep learning curve, but there are plenty of examples around the Internet, and it's certainly worth the investment.