Here are a few online resources that I've been using lately to study Japanese.
If there is a phrase I know in English, but don't know how to say it in Japanese, I'll search it on Tatoeba. The results are inherently more natural than trying to use Google Translate.
Also the built-in translator included in Chrome allows you to quickly translate entire webpages, making it especially helpful on sites like Mixi, with full Japanese interfaces.
Rikaikun for Chrome.
Furigana InjectorFor those sites with a lot of kanji. It puts furigana over words you don't know so that you can quickly see its reading. Allows you to customize the list of kanji to insert furigana on top of. Firefox / Chrome
YoutubeHere are a few channels that I like geared towards learning Japanese.