Japanese & Arabic are qualified as the hardest languages available to learn.
I'd say learn Spanish,French or Italian <-----Easiest available after English.
Not Japanese, try Chinese, Japanese is a simplified language of the Chinese language, some say Spanish is hard, true to a point, our grammar rules are stupid insane, specially when it is followed in the written form. Spanish to speak is easy, though you will get the accent wrong and also, the accent and some word definition vary from country to country, but in general it's all the same, if I would suggest, learn the one that they teach in Spain, because no matter what we all understand them.
Livemocha
It's a community backed language learning site, it features some of the theories used in Rosetta Stone, you can't be ashamed about submitting a vocal input to verify if your pronunciation is correct, you will also need some external reference(Dictionaries, Grammar Rules, etc.).
In overall it's a good site, if you make a profile, be sure to check the background of the user you ask help from, they have a score system to let uses know, plus they verify if the member is legitimate, since many claim they are teacher, translators or language Enthusiast.
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This spanish will do me fine. "mi no hablos espanol" :>
Anyway.... Buenos dias (spelling?)
"My no speak Spanish?" that's what it translates.
the other one is perfect.