Road Cycling - new to biking

I am new to road biking and need some advice on the best bikes for the money. I am considering Cannondale, Trek and Specialized, slightly above entry level bikes. What brand would you recommend? Also what features are especially important?

What do you want to do with the bike:
Competative racing, keep fit, long day rides, commuting /touring ?
What is your terrain like, flat or hilly?
Will you be riding in winter or during wet weather?
What size are you, do you have any riding experienceand how fit/athletic are you right now.

All of these factors have a bearing on what kind of bike is best.
The "normal" road racing bike is best for competition and fitness riding, but its not always the best bike for everyone.

I am interested in triathlons and fitness. The terrain will most likely be flat to moderately hilly. I'm 5'9", 130 pounds (too tall for female specific bikes). I like the Cannondale R500, but have read bad things about the headset? and the tiagra components.

Standard road-bike would be fine for your riding.
Look for a good fit. Bikes are normally fitted according to height, but the length is far more critical and harder to adjust. Fit and comfort are more important than the component mix.
A good bike shop will ensure that the final assembly and tuning is done properly. It may be better to pick the brand according to what your favourite shop sells.

There are no 'real' issues with the HS on the R-500. It's simply a cane creek threadless,that can eaasily be replaced with something better if the need arises. The HS on many bikes are less than desirable, and that's just the way it often is.Better than some of the integrated designs that leave you stranded with one manufacturer or standard.The cdale is good bang for the buck for what you are looking for It fits. 105 components might be better long term, and Giant anf Fuji often offer better bang for the buck than some of the bigger names.

Haley;

Buy for fit. A womans body is different porprotioned than a mans (praise God) and the standard fit doesn't work. A lot of bikes that are the right height are too long and you will never be comfortable.

If you're planning to race your bike, and have the cash, I recommend stepping up a level in frame and components.

About a month ago I bought a Cannondale R700 USA Edition. I had my LBS build it up with Ultegra components, Mavic CXP-33 wheels, and Michelin Pro tires. This bike is incredible! Cost was around $1,500, and worth every penny. I've put about 400 miles on it already.

I also recommend having a LBS fit you properly for the bike. I'm 6'4" and ride a 58 cm bike. Most people I talked to assumed I would need a larger frame, but my body geometry would not have supported it.

Hope that helps.

All the brands you mentioned probably make a bike in your price range that will be more than suitable for your needs at this time. I agree with Pokey that Giant makes bikes that are a good bang for the buck. Since I think that Tiagra components are fine for someone new to the sport - you can always upgrade parts or bikes if you really push your equipment - you may want to compare the 2002 Giant OCR2 with the other bikes you are considering. As others have already said, go with the best fit.