Looking for used bikes

hey, here are a few bikes (new) for less than $600:

http://www.bikesdirect.com

you can get a bunch under that price and shiopped free! 

I highly recommend the guys @ All3Sports in Atlanta.  They are located in an office park off of 400.  www.all3sports.com  They have been a huge help to me with getting started.  Bill spent over an hour getting me set up in the right position on my new Scott.  Definitely check them out first.  

I echo that All3sports is a great shop and the bike guys are VERY knowledgeable but all their bikes are way out of the OP's price range.

I would continue to check craigslist because there are decent bikes listed on there but you have to act FAST if you see one. Also, you could check ebay and just limit your search to within 100 miles - or however far you're willing to drive. Also, check with local shops and see if they know of anyone selling a bike. Roadies are notorious for upgrading so lots of times they'll sell a perfectly good, entry-level or just above, bike for a decent price.

Good luck in your search! Getting a new bike is overwhelming and exciting!

 If you found a used tri bike at All3Sports in the $500-600 price range, I think I will run over there and get one.    

 pmazer, If you are on a budget you may want to think about your goals.  You do not necessarily need a tri bike.  I still use my road bike on tris and I have been doing them about three years.  You may want to think about getting a used road bike for a year or so or forever for that matter.  ALL3Sporsts does not have any used tri bikes that I know of and I do not think you will find any find any bikes there in your price range.  I would scourge the internet as you have been doing.  Roswell bikes always has a supply of used bikes including tri bikes.  They may have something used in your price range.  As I mentioned earlier, think about your goals.  If you are interested more in speed or your health and having fun.  Speed cost money and work.  Health and fun come with much less money cost.  There are casual athletes on here that spend your price range on wheels in an effort to get a little more speed.  I have also seen guys on mountain bikes passing guys on pretty nice tri bikes. So, think about what you want and go from there.  I would suggest getting  something off of the internet and possibly checking out the used bikes at Roswell Bikes. 

I was at Roswell Bikes yesterday getting some tubes for my tires and noticed that they had a good selection of used tri-bikes, especially if you are a guy.  It's worth a drive up there to see if they have what you need.

 Also, don't be afraid to shop the internet.  Doug found his QR and my K2 tri bikes very cheaply online.

If you want to get a lot of bike for your money you'll need to do a lot of work yourself.  Search the net for write ups of fit and models so you'll know all the details when you see the right bike come along.  I bought mine on ebay and my wife's off the net from a retailer on closeout.  I saved about 50 percent off retail and I felt like this was worth doing the above research. 

From what you said in the original post I would look at road bikes.  There are more used road bikes out there so the prices are generally better.  Look for one with shimano 105 or better with new cables and you will be a happy camper.  One last thing,  don't forget to budget shoes and cleats.

This is a site that does a good job "fitting" you:

http://www.competitivecyclist.com/za/CCY?PAGE=FIT_CALCULATOR_INTRO&INTRO_LINK=NOREDIR&SITE.CODE=TRI

If you are planning to get a bike fit after you purchase the bike, then you might be able to ask the fitter for a size recommendation.