All you guys advocating immersion as the best way to learn a language are 100% correct. Unfortunately, many of us don't have the time or money to immerse ourselves in a language, especially when we're learning a language as a hobby. This doesn't mean that only people who are able to immerse themselves in a language should be able to enjoy the joys of learning a new language. The best language learning tapes/cd's/computer programs/etc... are the ones that replicate the immersion process as best as possible.
Where can you get the FSI/Barron's stuff?
And as a slight aside, when you talk about native fluency, that includes more colloquial ways of speaking right? A lot of problems with lessons (especially prepared lessons) is that they stick to a too formal style that no one really uses.
You can purchase the Barron's stuff off of Amazon. I buy 90% of my language materials off of Ebay. Even if you lose an auction, some opportunistic vendors (who notice that you lost an auction for language materials) will contact you to see if you want to buy some steeply discounted tapes and CDs.
Native fluency means speaking instinctually (like most of us do with English). There's little to no hesitation and your accent, intonations, and tone replicate that of a native speaker. It does include colloquialisms.
My criticism of the Pimsleur involves the Pimsleur method of graduated recall. It works GREAT for pounding vocab words into your head but you wind up learning phrases that aren't realistic. Here's a quick exaggerated example of how the process works:
Phrase 1) Jack and Jill went up the hill to fetch a pail of water.
2) Up the hill went Jack and Jill to fetch a pail of water.
3) Where did Jack and Jill go to fetch a pail of water?
4) To fetch a pail of water, Jack and Jill went up the hill.
5) How did Jack and Jill fetch a pail of water?
6) Jack and Jill fetched a pail of water by going up the hill.
Obviously, some of those phrases would never be used in everyday language. Pimsleur is a great (albeit expensive) method of getting familiar with the basics of a language. Personally, I always use a Pimsleur language series prior to visiting a country for vacation. I recently used the Pimsleur Greek CD's prior to going to Greece (rented it from my local library for free). It helped me out a bit with the basics (asking for restrooms, thanking people, asking for directions to the Parthenon).