If you're like me, you've already spent a ton of money on your costumes, your badge, and your hotel room, and now you're looking for ways to cut costs. There are all kinds of ways to save money at DragonCon, but many of them involve violating the rules in some way, such as not buying a badge, sleeping on the floor in a hallway somewhere, etc.
However, the one thing you can do that is totally not against the rules is eat for free. It requires a little self-discipline and a willingness to eat whatever is offered, but other than that, it's pretty easy.
First, and most importantly, many conventions have what is called a "ConSuite". This is a room that anyone with a convention badge can enter, and they serve free food and snacks throughout the day.
DragonCon has a con suite, and it's located in room 226 on the second floor of the Hyatt Regency hotel, above the food shop in the lobby. There's even a little stairway next to the food shop that takes you right up to that area. If you're confused, on any given day of the convention, you can probably just follow someone else, as there's usually a semi-steady stream of people going to and from the con suite.
Above: ConSuite from DragonCon 2006 by Wing Commander
The food in the con suite ranges from things like chips and hot dogs to donuts and cookies, but there can be all kinds of odd things like cake, meatballs, or who knows what. If you want to eat for free at DragonCon, the best thing to do is visit the con suite immediately upon arriving, and ask someone who works there what their schedule is. That way you'll know when to arrive each day. The con suite is a vital part of eating for free, and you absolutely can't do it without it.
Second, there's the food court in the Peachtree Plaza. The Peachtree Plaza connects the Hyatt and the Marriott hotels, and it features a wide selection of fast food options, including Chick-fil-A, Subway, and a whole host of interesting choices. However, last time I checked, you have to pay for fast food, right?
Above: Food Court at DragonCon 2011 by American Comicon
Well, in the Peachtree Plaza, there are a variety of those fast food restaurants that sell an assortment of marinated chicken-and-rice dishes, and each one of them has a worker standing out in front of their store handing out free samples during peak hours. The number of restaurants varies from year to year, but there have never been less than three. Sometimes there are as many as five.
It's incredibly simple to walk through the food court taking free samples every hour or so during the afternoon and early evening. I wouldn't advise against doing it any more frequently than that, because the sample-givers will probably start to recognize you at that point, and they may not want to give too many samples to the same person. So space out your samples, and you can fill yourself up on chicken!
Between the food court free samples and the con suite, you should pretty easily eat enough to provide all of the nutrients your body needs for the extended weekend.
I hope that helps!
Cover photo at DragonCon 2010 by futuregirl
EDIT: Several people have made some excellent suggestions since this was published. Sheyne Fleischer of the League of STEAM suggested that if you donate blood at the on-site Red Cross booth, they give you free juice and snacks. I advise against doing that more than once in the weekend, for the sake of your health!
Also, Emilie Pormen Bush, who wrote the children's book Steamduck, reminded me that room parties will often have food for guests, though it can be hard to find an open room party. Book-launch parties in particular are open to the public, and usually have a nice spread. So keep an eye out for them!