Working with LaTeX recently, I found a site dedicated to diagrams produced with LaTeX:

http://www.texample.net/

A couple of examples:

http://www.texample.net/tikz/examples/dipolar-magnetic-field/

http://www.texample.net/tikz/examples/pascals-triangle-and-sierpinski-triangle/

http://www.texample.net/tikz/examples/polarizing-microscope/

http://www.texample.net/tikz/examples/radix2fft/

Amazingly beautiful diagrams.