Graham Oppy is a good philosopher at Monash University in Australia. He's also a careful and incisive critic of theism in general and Christian theism in particular. He's recently come out with a comprehensive critique of theism in his new book, Arguing About Gods (Cambridge University Press, 2006). He's also recently come out with another book, Philosophical Perspectives on Infinity (Cambridge University Press, 2006), which includes very careful critiques of William Lane Craig's philosophical arguments for a finiten past.
His criticisms are often very powerful, although often very compressed, which (I think) accounts for why his criticisms are sometimes overlooked. I highly recommend his online pieces, here, which range from criticisms of standard arguments for the existence of God to book reviews of Christian apologetics books.