Solid versus waves
Because I was on vacation late last week. :^)
Joe Davis of MIT has also advocated sending messages through the galaxy via DNA:
http://www.viewingspace.com/genetics_culture/pages_genetics_culture/gc_w03/davis_joe.htm
And Christopher Rose and Gregory Wright have argued that "solid" messages (artifacts) would work better and last longer over interstellar times and distances:
http://www.winlab.rutgers.edu/%7Ecrose/cgi-bin/cosmicB.html