What are the best resources for learning Arabic?

If you're a beginner and want to learn alone then you might want to check out these two websites: http://www.madinaharabic.com and http://www.learnarabiconline.com.
But in my opinion, the best way to learn any new language is by practicing it with native speakers.

Try buying self study lessons ( Like Pimsleur, Arabicpod101.com), the find an online teacher to practice with if you're not in an Arabic country or have no access to Arabic people, do online language exchange ( even better if its face to face), listen to songs with subtitles to see how the different uses of simple words, Watch a movie, why not !!(with subtitles...) Best way to learn Arabic, practice, practice and do more practice...

If you're a translator and want to be better in Arabic, I think the best way is to read newspapers, because the best Arabic language nowadays is used in the news.
You can also read books for well known writers, but I prefer Arabic newspapers as a fast and very effective solution.
I hope this helped you.
Good luck!!!

You can try http://www.learnarabiconline.com,

There are two types of language learning one is Colloquial language which can be learned being among natives but as far as Literal language concern, so it needs good teachers who can teach dedicatedly, even though so many technology development but the learning which comes from school can not be overlooked, moreover learning arabic language is not similar to other languages.
For commercial purpose anyone can learn some basic sentences thru person or internet etc.
but learning in deep this language needs good teacher who can explain and teach grammer etc.