One of the hands-down best online resources for the bible is Skeptic’s Annotated Bible. I like it because it lists a huge number of biblical contradictions and the like, and also links to Christian responses to these problems.
Some of the claimed contradictions aren’t such a big deal, and Christians are able to come up with reasonable explanations for them. But not all of them, for sure. That’s where Skeptic’s Annotated Bible comes. Because you’re able to see both points of view, it is fairly easy to tell when the contradiction in question is resolvable and when the Christians have no choice but to resort to strained explanations to clear things up.
The website has now been made into a real live Bible. It looks a neat little item to own, and probably very useful for debates.