Also helpful is anything that explains that a baby in the womb is a distinct human being, not merely a part of a woman's body. Obviously I'm talking with people that are pretty far gone to the other extreme, but these are persuadables, not activists.
That's easy. Do a DNA test on the fetus, and compare it to the woman - it is NOT her body, as simple science illustrates.
Here's the section on fetal pain
http://www.abortionfacts.com/online_books/love_them_both/why_cant_we_love_them_both_14.asp