On a budget: See this report for smart spending ideas.
Inspirational ideas: This website gives you a list of all the Halloween trends AND shows if the trend is up or down in popularity.
Lady Gaga: Oh how she gave us so many ideas from this past year! Here are official Lady Gaga costumes.
Glee: Check out this site to get all the insights for clothing necessities, props, and catch phrases
Op-Eds: Of course every blogger [including yours truly] likes to blog about costume ideas, costume trends, and their own ideas. You can see one here and here and here... and oh, yeah here. Promise, they're all great reads! [And don't forget about Farmeville this holiday!]
Scary Movies: Scary movies are all about Halloween. While you may not be inspired by the costumes directly, you may be inspired by the scary season. Just in case you need some inspiration, be sure to check out "Pretty People, Scary Movies" *costume ideas not guaranteed.