I've just had a browse through the 'study aids' pages of www.jbox.com, which is a great way to stimulate ideas. I've bought a few things from there over the months:-

-- A couple of issues of Nihongo Journal (日本語ジャーナル), the sadly discontinued magazine for learners of Japanese. The content ranges from beginner to advanced level, with articles, tips, exercises and a CD. Back-copies are available from jbox.com and from the publisher's own site:- www.alc.co.jp.

-- A book called Catchy Japanese Phrases. If I wanted to know how to say: "I have a hangover", here's where I'd look. The book is divided into subject areas, such as Eating and Drinking, Greeting & Weather. Each phrase is printed in English (plus Chinese and Korean) on one side of the page, and Japanese (kana/kanji and romaji) on the back of the page. Thew pages are lined off into 3 sections. If you remove the pages from the book and cut them into 3, you have flash-cards. There's even a printed circle where you can punch a hole to keep the cards on a book ring. Sheer genius.

-- 'Pass the Test' headband (Zettai Goukaku Hachimaki) - Indispensable.