If you want to make me happy by supporting Firefly, here are some ideas:
Go to http://www.fireflysupport.com/ - they have all the latest updates and addresses. Currently, they suggest sending snail-mail letters and/or postcards to UPN, encouraging them to pick up Firefly. See bonibaru's letter here.
Read creator Joss Whedon's bulletin board post here, courtesy of debchan.
Tim Minear is the other co-producer with Joss Whedon. Check out his site here: http://timminear.net/
Read Firefly vs. the Firing Squad at teevee.org