Probably my favorite Catholic blogger, Mark Shea, has a fine piece up at Inside Catholic which analyzes the biblical evidence for the Perpetual Virginity of Mary. You can read that article here. This is ironic, since a couple weeks back, I finished reading his Mary, Mother of the Son trilogy of books, which I found to be both informative and witty. I highly recommend all three. In particular, the first volume, Modern Myths and Ancient Truth, spends a great deal of time setting the table, so to speak, looking at not only the ancient Christian and non-Christian philosophies, but probably more importantly the a priori assumptions about the Catholic Church's Marian teachings made by those who oppose them. Only at that point does Mark move to volume two to begin analyzing the four major Marian dogmas in depth. Volume three is concerned primarily with Marian devotions and apparitions. Again, I highly recommend all three volumes.