Korean pronunciation resources

I am being beat down, and then stomped upon, by Korean's tense consonants. I'm looking for some resources that will help me practice outside of class. (The textbook we're using doesn't really explain anything and didn't come with audio, which I really want.)

So, does anyone have any recommendations for introductions to these consonants? I'd prefer something online, because I'm cheap, but if you're a fan of a particular program then I'll look into it if I continue to have trouble.