Here are some webpages that I found that contain tons of helpful tips and resources for cosplaying.

If there is a webpage that you have found to be helpful, then please let me know and I'll add it to the list here.

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InuYasha Cosplay - Tips on how to dress up like the characters from InuYasha.

How to dress like Soujirou

The Costume Connection - Has a couple of good Japanese clothing patterns.

Round Earth Publishing - Japanese clothing patterns.

Instructions for making Hakama

Knowledgehound: Costume patters, tips, and tutorials - Lots of helpful information about Japanese clothing and Harry Potter costuming.

Knitting in Harry Potter - Instructions on knitting the scarfs and sweaters from Harry Potter.

Ebay.com - A great place to find costuming materials, as well as already made costumes and props.