I speak English (obviously) and Spanish.
Some may say I also speak a lot of BS.
Still, assuming the OP is sincere, I have heard that Rosetta Stone is a very good set of programs.
Of course, 99% of the people who are reading this site are probably taking a second language as part of their HS curriculum, so the Rosetta Stone (and other programs like it) would best serve as supplements (or primaries for their parents!

)
Speaking more than one language is an ability that cannot be overvalued. It is simply the best thing you can do.