I have a feature story in the new issue of Mother Jones exploring the U.S.'s "material support" laws", which have become the U.S.'s most frequently used anti-terrorism laws. They have also served as the basis for many of the government's most questionable terrorism cases, for instance that weird purported plot by the "Seas of David" to blow up the Sears Tower.
Basically, these laws (there are two) are far more expansive than most people realize. And I argue that one of the reasons these questionable cases keep getting prosecuted is that the material support provisions give prosecutors a shot at conviction even when the evidence adds up to quite little. In any case, if you're interested here's the piece.
P.S. I've been on a couple of radio programs plugging the article. You'll eventually be able to hear the first show here (about one hour and 20 minutes in). I was also on Air America last night but can't seem to find that online, which, ahem, is just as well.