A campaign has now been launched to raise awareness of this target -- currently we have over 380ppm of CO2 and it's going up faster than ever before -- http://www.350.org/
350.org Postcard Campaign
The Reality Report interviews Jamie Henn of 350.org, a creative new initiative formed following the scientific understanding that atmospheric greenhouse gas concentrations need to be reduced to at most 350 parts per million.
See also the Climate Code Red book and audio from earlier in the year -- this is essential listening and reading: http://www.indymedia.org.uk/en/regions/sheffield/2008/02/392071.html
And James Hansen's site: http://www.columbia.edu/~jeh1/
And the article on Real Climate on James Hansen's paper, Target CO2: http://www.realclimate.org/index.php/archives/2008/04/target-co2/