The christian astrophysicist Hugh Ross has a very interesting website called Reasons to Believe.
http://www.reasons.org/
Since Ross approaches the discussion of origins from an astrophysics point of view instead of life science, there will probably be some arguments there most Christians haven't come across before, for example. A lot of Christians won't agree with him because he doesn't support young earth creationism, but he does argue that astrophysics exposes evolution as false.
Also, if you search "apologia church" on youtube, you'll find a bunch of footage of this guy named Jeff Durbin speaking with athiests about the existence of God. You might pick up a few things you can use from him. I don't agree with everything he says, but the "raw" footage videos he has can be useful in lots of ways. Generally, I think he conducts himself well. He mainly deals with philosophy though, not science.
In general, I agree with the sentiment Ph8th (I'm guessing?) proposes, which is that you can't "prove" people out of their beliefs. But, I also am forced to recognize that philosophers and scientists do sometimes turn to God as a result of studying their fields, so I can't say that God won't use such a discussion to draw people to Himself.
I have no idea at all how you plan to go about having these sort of discussions, but I do know that I started out having them the
wrong way. Overall, I think it may be helpful to keep in mind as you have these talks that the love and compassion of Christ are more likely to plant a seed than humiliating another person publicly with a barrage of proof.