If you're looking for Yu-Gi-O cards, here are a few possible places to buy them online:
Pokeorder carries a wide variety of Yu-Gi-O Single Cards, Booster Packs, and Theme Decks.
CrossToy has a more modest collection available, but offers Yu-Gi-O booster boxes for sale, which are much cheaper than buying the boosters individually.
Or, check eBay for Yu-Gi-O:
Yu-Gi-O Video/DVD
Amazon is a good place to find Yu-Gi-O videos and DVDs or even books and computer games:
