Our Angie's List Magazine staffers produced a good comparison piece a few years back comparing the pros and cons of concrete vs. asphalt driveways, including the cost. The info, of course, is a bit dated (2010, 2011), but it should provide at least a starting point for you.
According to the experts quoted in the articles, $5 to $10 per square foot is a good starting price to consider for a basic concrete driveway installation. Again, that info is a bit dated and prices only seem to go, and don't forget that factors such as installation site, the existing driveway and other factors will likely affect the price.
If you're looking for more info on concrete driveways or other projects, try searching our library of articles at www.angieslist.com/search.