Learn Japanese #1 Web resources
This one here is a site which will convert kanji into hiragana or romaji and give the english meanings as well as a details about the particular word. (I think this is the best and most accurate translator I've come across so far)
** This is another excellent dictionary for not just words but terms and phrases: http://www.animelab.com/anime.manga/dictionary
***The same site as above also has a decent translation tool: http://www.animelab.com/anime.manga/translate
The next site is very useful for studying for the JLPT (lvl 4-1, 1 is the hardest). They have past exam papers, listening comprehension material and various quizes too.
Another site with JLPT learning material:
Crash course in basic Japanese
An audio phrase book.