Dreadtime Stories are a series of horror audio dramas by Fangoria magazine that they make for free over the web for one month, and sell the back catalog for a pittance (~£1 for a download). They're very much in the vein of an anthology horror movie (like my dear beloved Creepshow, a cheesy horror movie I used to while away evenings watching) crossed with classic American old time radio. They feature Malcolm McDowell, an actor with a sci-fi career so distinguished that his characters have killed William Shatner (Star Trek Generations) and Mark Hamill (Wing Commander IV, if you lose) as the narrator at times putting on a bit of an American drawl, though perhaps that's because he's been over there so long.
The current one for streaming as of July, 'Mercy' isn't exactly typical of the stories but is fairly ghoulish if a bit obvious in its execution. Probably my favourite one is "A Fungus Among Us", which is a very nihilistic classic horror-thriller in audio format.
The acting is a little hokey (people don't speak naturally, perhaps it's because I'm a Brit, and seem awfully ghoulish) and there is quite a bit of gore for audio, but it's well worth a look. I've listened to all 10 of them now via the stream and Audible.
Also by the same repertory company is the Twilight Zone Radio Show. I was a little disappointed with this in the sense that the website said it was a reimagining of the Twilight Zone for audio, with modernised stories. Most of the stories are retellings of original Twilight Zone episodes and are not updated. They feel amusingly like 1960s period pieces.
Mind you it does seem a bit of a shame there isn't a Twilight Zone/Horror Short anthology show on television these days.