The most effective (and legitmate) organisation in the US I've seen so far is www.eff.org

In Canada, I follow where Dr Geist leads http://www.michaelgeist.ca/

Geist also edits a newsletter summarizing the international news regarding IP law. I've found it gives an excellent snapshot of the way the whole IP law mess is shaping up internationally.

Subscribe at http://www.bna.com/ilaw/