Check out this cool design at Threadless called Mercury Rising.  Obviously a commentary on Global Warming and the threat it poses to Polar Bears.  This t-shirt's not going to save the world, but we have to give kudos to them for helping spread the word.  As silly as it is, there are people out there that get most of their current events from reading t-shirts and bumper stickers.  I should mention, it's not a t-shirt or a poster yet but they are still taking votes so go make your voice heard.  For those of you not familiar, Threadless makes t-shirts and posters from user submitted designs.  Ever few weeks they pick the top 10 designs and put them into production.  Sort of a design democracy, but they do wield veto power.