Amazon Japan:
http://www.amazon.co.jp
Use the Google Chrome browser to help translate the pages for you automatically. And if you type Romanized characters (romaji) into Amazon.co.jp search, it will find things even though most products are listed in native kanji symbols (maybe hiragana, but mostly kanji). For example, "Macross Frontier" brings back the results for
マクロスF -- note that your browser has to support Japanese to see the characters I just typed. Remember to search for original Japanese names, not the later American renames. Kenshin vs Samurai X, for example.
... and yes, this means I do know a little bit of Japanese. Very little. But I've been studying it for the past couple of years, off and on, as I find free time. It's a really awesome language, to be honest. I can appreciate some of the artistry, as well as the Spanish-like conjugations for respect, or even the grammar rules that put subject/object before action.
And eBay.com, of course:
http://listings.ebay.com