Read here, link to the signatures at the bottom.
The important thing is to 1) sign, 2) PASS IT ON-- blogs, facebook, twitter, etc.
I cannot tell you how important it is to pass it on.
People say that online petitions don't do anything.
By themselves, they don't.
But under certain conditions, they do create public pressure, and a certain atmosphere.
Twenty years ago, the bishops didn't even TALK about abortion. Now they do. This is partially due to pressure from the faithful.
We have to keep it up. It's not the petition by itself that does it, it's the cumulative effect of all our actions.