If you like creating or buying costumes for cosplay, then you probably also want to see where you can wear them. Of course, there are tons of opportunities around Halloween. Basically any type of Halloween party is an opportunity to go out in your favoriate cosplay outfit. But if you are looking for a larger type of gathering there are a bunch you can go to.
Some are Sci-Fi themed, some are historical themed like RenFaires. I am going to give a few links to each of the main Cosplay Events and a brief description of each.
Ren Fair
Renaissance Fairs are geared towards people who like dressing up as Maids, Knights, and other figures from the Medieval era. Most of the costumes are going to be historical based. You will see outfits that look like they are from a Shakespeare stage play. Unlike lots of other cosplay events, you don't see lots of makeup or body paint at a Ren Fair.
The great thing about the RenFaires is that they are held all over the country. Many of the large Cosplay events are only in one location (ComicCon, Dragoncon) so if you don't live near the area it will be a big trip.
Here is a list of Renaissance Fairs
http://en.wikipedia.org/wiki/List_of_Renaissance_fairs
This site will give you some more information about the current Ren Faires
http://www.renfair.com/index.asp
If you are looking for some ideas about what to wear at a Renaissance Fair then these are two cool sites
http://www.westword.com/slideshow/50-best-costumes-of-the-colorado-renaissance-festival-30702305/
http://keepcalmandcrafton.blogspot.com/2011/04/renaissance-fair-costumes.html
Dragon Con
DragonCon takes place in Atlanta every year. It is one of the biggest sci-fi conventions. Lots of people go in regular clothes, but there are also lots and lots in cosplay. In fact, it is a bigger cosplay event than probably even the RenFair. You will see people in everything from Gladiator costumes to cartoon and superhero costumes.
Here are some pages with examples of DragonCon Cosplay
http://io9.com/5940438/ultimate-proof-that-dragoncon-has-the-best-cosplay-on-earth/
http://collider.com/cosplay-dragon-con-images/
The Official Site
http://www.dragoncon.org/
Some more DragonCon photos
http://www.geeksaresexy.net/2012/09/06/more-photos-from-dragoncon-2012/
Comicon
ComicCon are a group of comic book fan conventions. They happen in a bunch of different cities.
The big one occurs in San Diego
Here is a link to the San Dieago Comic-Con site
http://www.comic-con.org/
There are also conventions in New York, New Jersey, Dallas and a bunch of other cities
This link gives you the list of cities.
http://en.wikipedia.org/wiki/Comic-Con
Here are some photos of the cosplay ides from Comic-Con.
http://www.theguardian.com/culture/gallery/2013/jul/22/comic-con-2013-costumes-in-pictures
http://www.ign.com/articles/2013/07/26/comic-con-2013-cosplay-battle-winners
http://thechive.com/2013/07/22/the-best-comic-con-costumes-of-2013-51-photos/
Halloween and Dorm Parties
Of course, you don't have to go to a big convention or RenFair to dress up. Most people only do cosplay for Halloween. It is popular in colleges also. There are lots of costume parties. Girls like everything from sexy wonder woman costumes to the classics like Tomb Raider or Sexy Vampires like Kate Beckinsale from Underworld.
