Rosetta Stone sucks, don't go anywhere near it. Pimsleur & Michel Thomas are nice, particularly if the length of one lesson is equal to one half of your daily commute.
At the core of AJATT are the following principles:
1. Total immersion
2. Use of an SRS (Anki is free, cross-platform, & open source) to learn vocabulary IN CONTEXT
3. Language exchange with a Skype buddy to work on pronunciation
I don't know if #3 would be adequate for mastering Arabic pronunciation though. Japanese pronunciation is relatively easy for native English speakers so it's not an issue, but you might have to find somebody IRL to help you out.
AJATT's a great website for learning Japanese - you might be able to adapt it to Arabic: http://www.alljapaneseallthetime.com/
At the core of AJATT are the following principles:
1. Total immersion
2. Use of an SRS (Anki is free, cross-platform, & open source) to learn vocabulary IN CONTEXT
3. Language exchange with a Skype buddy to work on pronunciation
I don't know if #3 would be adequate for mastering Arabic pronunciation though. Japanese pronunciation is relatively easy for native English speakers so it's not an issue, but you might have to find somebody IRL to help you out.