I've had three folks in the last month ask me about how to buy a bike. Here are the three pieces of advice in order:
# "Materialpost.com":http://materialpost.com. John Gallagher runs this group. For $150, you will actually get a bike that fits you. Believe it or not, this is about 80% of the performance and comfort on a bike. So, you can have Lance Armstrong's bike and it won't help if it doesn't fit and a guy on a $200 20-year-old bike will whip you if his fits right. Give John a call, he'll do a fitting, adjust your current bike as close as possible and then sit down with you on the web and give you a list of bikes that will really fit like a charm. He's also a huge seller of custom bikes so you can get a custom made one.
# "Gregg's":http://greggscycle.com or Montlake Bike Shop are two of the best dealers in Seattle. If you don't know much about bikes, you can go there and they'll take care of you. They charge a little more, but it is worth it if you aren't a do-it-yourselfer.
# "ebay.com":http://ebay.com. If you are a do-it-yourselfer and don't mind the risk, then ebay is a great place to get a used bike. There are plenty of folks who will buy a new bike every 1-3 years or who own 4-6 bikes and are selling. Also, racers sell the bikes sponsors give them. The discounts are anywhere from 30-50% off, but it is caveat emptor. Still, if you don't mind setting things up yourself, not a bad option.