DragonCon is by far the largest convention I've ever gone to. It takes place every year during Labor Day weekend in Atlanta, Georgia. I like to think of DragonCon as a cosplayers' convention.
There is absolutely no limit to what costumes you'll see on the convention floor. Because DragonCon is a multi-genre event, the costumes range from comics, cartoons, films, TV, anime, music, video games, renaissance, current events...just think of it as Halloween on steroids.
(Check out these pictures from last year's DragonCon)
DragonCon is the only convention I've been to that hosts a huge costume parade every year. All the cosplayers divide into groups (by either costume clubs or just costume genre) and march down Peachtree Street in downtown Atlanta.
The first year I went to DragonCon, I participated in the parade. I wore my Power Ranger costume, so I thought it would be appropriate to march with the super heroes. I was overwhelmed by the crowds that came out to see all the costumes. Aside from sweating like crazy in my helmet under the hot Atlanta sun, I had a blast.
I just found out that the PBS in Atlanta is doing a documentary called "Four Days at DragonCon." I watched the preview that they put on YouTube, and I think it's a wonderful look at what the convention is about, and what kind of people attend. Any documentary about nerds can easily make us all look like weirdos, but I think this is definitely worth watching.
I will be attending DragonCon this year, and I'm counting down the days. I won't have a computer with me, but be sure to follow me on Twitter @NashNovaCosplay. I will be tweeting and sending pictures throughout the con, and during my 13hr. road trip from Chicago to Atlanta.