I concur with the person who suggested Rosetta Stone. It can be a little on the expensive side, but luckily I got mine for free. Yeah, it won't teach you all the slang words and otherwise improper usage of the language that really comes to be part of the native dialect of a particular place, but it really does an excellent job of teaching you the fundamentals and how to actually 'speak' the language vs. merely listening to it. There are hundreds, if not thousands of those learning software CD's out there, and I've tried several of them, but Rosetta Stone has been the best so far.
It's kind of akin to teaching someone very proper English, but who the heck speaks that way? You have to learn the language first before you can twist it up you know.