I'm going to tell you something you might not want to hear, but (though I agree that the names dropped above have quite good SH's) don't take our word for it. In order to find the right story hour for you, make sure you sample a stuff not only from the big boys, but the new guys too. I also warn you that, depending on your preferences, not every story hour will be for you - while some will appeal to your personal tastes, others will not be up your alley, regardless of how well they are written (there are a handful of very well written story hours that I haven't been able to immerse myself in, simply because the tone wasn't for me).
That being said - there are a ton of good story hours out there - don't be afraid to sample them, even if all you do is read the first post or two. Oh, and make sure you take a gander at ForceUser's story hour: its set in a campaign world that's modeled on historical SouthEast Asia. I've never seen anything like it, and it rocks.