TikZ/pgf is a really nice way of making LaTeX graphics. Unforntunately, v2.00 is not yet included on MacTeX, but upgrading turned out to be easy: ``
oums-qipvis:~ janus$ mkdir -p Library/texmf/tex/generic
oums-qipvis:~ janus$ cd Library/texmf/tex/generic
oums-qipvis:generic janus$ cp ~/Downloads/pgf-2.00.tar.gz .
oums-qipvis:generic janus$ tar -xzvf pgf-2.00.tar.gz
Update 20080807: As Kjell Fauske points out in the comments there are CVS snapshots of pgf at www.texample.net/tikz/builds/.