As for deliberate messages to the stars...
We have sent out a few, starting in 1974 with the famous Arecibo
Message to Messier 13:
http://en.wikipedia.org/wiki/Arecibo_message
There have been a few other Active SETI projects in the
following years:
http://www.cplire.ru/html/ra&sr/irm/index.html
http://www.cplire.ru/html/ra&sr/irm/Making_a_Case_for_METI.html
Very long-term response deliberate messages have also been
sent via the Pioneer and Voyager probes:
http://en.wikipedia.org/wiki/Pioneer_plaque
http://en.wikipedia.org/wiki/Voyager_Golden_Record
