Japanese Study
Websites to help you improve your にほんご
Speedanki
http://speedanki.com/
Tae Kim's Japanese Guide to Japanese Grammar
An excellent site that explains all the major grammar points.
http://www.guidetojapanese.org/
Excel@Japanese
A excel programme for learning kanji. Sometimes has a few bugs though.
http://japaneselearningtools.com/
Studyjapanese
http://www.studyjapanese.org/
JLPT Kanji Project
http://www.jlpt-kanji.com/
Jgram
http://www.jgram.org/
Hiragana and Katakana in 3 hours
http://www.geocities.com/Tokyo/Courtyard/3043/learningjapanese.html
Kanji Gold
http://web.uvic.ca/kanji-gold/
All Japanese All The Time
A somewhat unorthodox method that may help people who are struggling to improve.
http://www.alljapaneseallthetime.com
Meguro Language Center
http://www.mlcjapanese.co.jp/Download.htm
JEES-JLPT
http://www.jees.or.jp/jlpt/en/
JETRO
http://www.jetro.go.jp/en/bjt/
Yookoso
http://www.yookoso.com/
JapanesePod
http://www.japanesepod101.com/
Buy Japanese Textbooks Online
http://www.kinokuniya.co.jp/
http://www.amazon.co.jp/gp/browse.html/?node=337252011