Go to a shop and see what they have, don't buy anything yet.
Ask them about sizing, that's the most important thing. It's not a good idea to buy a bike without riding it first. Once you get out on the road and ride for a while, you'll begin to notice discomforts that weren't obvious at the store. So getting a bike properly fitted for you is a must...go to a good shop that specifies in road bikes. If you want to get specific, ask them about the difference in frame geometry among bikes.
In road bikes, small changes can make a big difference. For example...a 56cm frame is going to feel much different than a 54cm frame. So be careful and pay attention to everything on the bike.
Don't focus so much on brands; look at reviews. Go to roadbikereview.com and they'll probably have reviews for bikes you saw at the store.