I'm a marathoner that is interested in mixing in some duathlons and triathlons, but I am having trouble finding a starter bike (< $1500) made for a tall man. I am 6'6". Any brands and models that you can recommend that offer a frame that fits someone around my height?
At 6'6" you're probably going to be looking at the top end of most manufacturers size ranges, road frames of 62cm and above are the range you'll be looking at.
I said "probably" though, you would do best getting yourself to a local shop that knows something about fitting people to frames. Being so far from the average height I'd not risk buying something offline without having tried sitting on anything, particularly as it's your first road bike.
You really should go to a couple of good LBS's and get fit. They'll be able to recommend some different companies that make bikes that will fit your build. There are so many different variables besides just height that it's impossible to recommend a brand based on what you've given. You need to know your stack and reach in order to find the best geometry for you.
At 6'6", be wary of your local bike shop, unless you really trust them or they have a great reputation. Sounds like blasphemy to say that, but one of the problems you may have is that many manufacturers may not make a large enough frame for you and you will get sold the biggest thing they have from the brands they carry. Off the top of my head, in non-custom models, Trek and cannondale both make bikes large enough (I have a 6'5" friend on both of those), and I know for sure Specialized and giant do not. 63+cm would probably be your likely range, but a good shop with a fit that you will probably pay 100$ or so for should be able to help you dial that in.
Things other than frame size are important as well. I don't know your dimensions but you're probably wider in the shoulders than most, so you'll want handlebars that fit you well. Stem length is also partially driven by flexibility, so that's a consideration too. Also crank arm length can be tough for bigger guys, the expert in tall bikes is probably Lennard Zinn. He's a big guy himself and a custom frame builder, you may want to have a read through his site and consider some aftermarket options for those components.
Nothing "off the shelf" is going to fit perfectly for you. To mitigate, you'll want to experiment with long seatposts that have set-backs and long stems.
Since you're a marathoner, you're probably quite fit and are limber enough to deal with handle bars that are far lower than the seat. This lower stack height will also help you not be so cramped.
Eventually, you may want to get custom geometry ($$$), but tall folks can get by with frames that don't quite fit. The pros do it all the time.
SOMA makes good quality affordable frames and their ES comes in 66cm. I'm only 6'4 but long in the limbs and I rode that on an extended tour just fine.
The frame will probably set you back $400 or so which should leave room to kit it out.
Just about to ask a similar question, and figured I'd give you what I know so far. I'm 6'8", more torso than legs. 36" inseam, 37" sleeve in dress shirts.
Trek 1.5 is the low-end Trek road bike, aluminum frame, and comes in a 64 or 65cm setup. I have one. It works pretty darn well, out of the box. Both Trek and Specialized make bikes in this size, but not all of their bikes; that said, you're getting started around $1k.
Only change I made was upgrading the shifters on mine; they were terrible.
I had a similar budget getting started and at 6'5" and change found it impossible to find a local bike shop that could find a good fitting bike.
I started out with the KHS Flite 747: http://zinncycles.com/product/khs-flite-747/
You can get that for around $1600 and there are older models available for cheaper.
I measured myself and went with the XXL frame and then got fitted to the bike and the guy said I fit the bike great.
I'm now looking into possibly upgrading with a http://bikeclydesdale.com/ which has bikes made for taller riders with more customizations.