This is by far the easiest and most painless way to get started speaking in Vietnamese sentences and understanding dialog. I've been lending these lessons to everyone in my Vietnamese class, because they are so good.
The downsides are: they only teach you the Hanoi accent, which is the official dialect. People from Hanoi pronounce a bunch of different letters the same (r, d, and gi are all pronounced z) when they really should have different pronounciations. There is no reading or writing practice. And of course this is only the short and cheap introduction package which only has the first week's worth of lessons.
This is just the first 8 lessons (not 10 like someone else said) of Pimsleur's 30 lesson Vietnamese I. There is also a 10 lesson "compact" version, a 16 lesson version, and the full 30 lesson "comprehensive" version. The other versions are much more expensive. The 30 lesson version has finally been made now, so the complaint about it not being available is out of date.
Pimsleur language lessons use the same lesson plan for every language. Some other languages have level II and level III packages with another 30 lessons each, but Vietnamese currently only goes up to level I.
This is an audio-only system. Unlike other CD systems, you are only expected to listen to each CD once and then go on to the next CD. Each CD is a carefully designed lesson which incorporates revision into it. You are expected to listen to one half hour lesson each day. So this package will only last you a week. You will not learn a huge amount in one week, but you will be able to confidently use what you do know, and you will learn it very easily.
Paul Pimsleur was a great and famous linguist who has written many academic papers on language learning. So he knows how to teach. This is nothing like the CDs you get with other packages like Colloquial Vietnamese or Teach Yourself Vietnamese, it is far more like attending a one-on-one vietnamese lesson each day with a professional teacher.
Each half-hour lesson includes a dialog, practice of what you learned yesterday and new material. You have to answer all the questions out loud if you want to actually learn it properly.
The other great thing about lessons like these is that you will get a lot more housework done, since the audio-only lessons go well with boring physical tasks.
If you go to the [...] website you can listen to the first lesson of any language in real-audio, wma or mp3 so that you know what to expect.