The one's that seem most prevalent right now are that 1.) We need to have a god to have morals and since we do have morals there must be a god. and 2.) The universe is such an incredibly complicated thing that we can't really know anything for sure. Therefore it's plausible that there's a god.
Neither are sound arguments, obviously.
I have ordered a copy of Bertrand Russell's "Why I am Not a Christian" and it occurred to me that I have not read any recent arguments for the existence of god. For the most part, I usually try to stay away from the thinking that one must ALWAYS give all sides of an argument equal time regardless of their merit, but in this case it is interesting to see what the other side is thinking.
I found this website, not an authoritative site but it lays out the basic arguments on each side in a very understandable manner. The ontological argument for the existence of god is probably my favorite just for the fact that intelligent people have prescribed to such garbage thinking. http://www.philosophyofreligion.info/
I have an e-mail into a former philosophy professor of mine to see if he knows of any current arguments that merit time to read and when he gets back to me I will post his suggestions in this forum.