I have zero experience with it, but I've heard many good things about the Rosetta Stone software. As in, I know real life people who have used it and gush about it it.

I'm not able to judge their fluency, but some of them have been using it to learn a variety of different languages. The lady that lives at the neighboring farm speaks at least a dozen languages and she's learned all but two of them with the software.

She speaks passable French and Spanish (and English, of course) so I can vouch for the Spanish and the missus is fluent in French.