Almaany.com - قاموس المعاني
Just occurred to me that this website would be useful to some out there. I use it a lot (specially when translating technical and scientific terms between Arabic and English). It has other dictionaries but honestly I didn't try any of them except of the English part. The website in its core is actually a thesaurus (Mu'jam معجم), i.e. Arabic-Arabic, and it helps me as well.
Word: It doesn't work as Google Translate, as in translating a sentence, but it is word-based dictionary; As simple as that. Yet, it is far better than Google in my opinion, specially when it comes to scientific and technical terms. I think this website is supported by the Jordanian Arabic Language Assembly (just a thought, I'm not sure about this). So, hope it helps lot of you out there.
Tip: Thesaurus: معجم (Mu'jam)
Dictionary: قاموس (Qámús)