Shoes can be one of the most difficult purchasing decisions when becoming a runner. My first recommendation is to go to your local running store and have an expert fit you. The personal service and expertise can not be matched by the chain sport stores. You will pay a little more (sometimes) but the service is worth every penny! Keep in mind they love running even more than us average runners. They can provide you with great information about products, services and races that can be tailored to your needs. The store of choice for me (in the Detroit area) is Running Fit. Sometimes you just need an expert.
If you want some quick info before you go to the running store then I suggest checking out Runners World. Runners world has always given me great information when deciding on a shoe purchase. This link will take you to their Summer Shoe Guide http://tiny.cc/iutoy. In the meantime take the poll on the left side of this page and see what other runners have chosen.