I like
JWPce a lot for XP. You can look up the kanji by various means. It's free and it's also a handy reference when I know a word but not the kanji...type it in hiragana or katakana and it'll find the related characters.
However, if you have little or no experience with Japanese, it can be rather difficult to make sense of words (especially verbs) in formal styles of writing.
ganbatte!