... to do if you're in the United States, and concerned about
this.
It may get you arrested - but I think we're well into the stage now where people have to start risking arrest to make a vital point. I'd do it, but I think flying to the U.S. for it would kind of defeat the purpose. And there isn't anything equally meaningful planned in Europe, AFAIK, at the moment.
Invitation and details here. Background info on the tar sands
here.
Please spread this around if you think there may be even just one person on your flist who might be interested. This kind of thing works better the larger the number of participants.