You might search "Podcast Audio Dramas" and "Sci Fi Podiobooks" too.
For audio dramas, I'm involved in a miniseries to be done by producer Bill Hollweg* at
BrokenSea audio called
2109: Black Sun Rising that's due out in the next six months or so. They've got a
Jake Sampson series that's something of a pulf sci-fi revival. They've also got a
Planet of the Apes fanfic series that is brilliant and has received applause from the original creators of the movies.
Hidden Frontier will be releasing a monthly Star Trek fanfic production at any moment now called
Star Trek Equinox.
Pendant audio has various original sci-fi series. And don't miss Christof Laputka's
Leviathan series. It's so brilliantly produced it hurts. Finally, I've already bragged about the
Must Be Nice Studios remake of
Who Goes There? a.k.a.
The Thing, so I won't push it more here.
http://mustbenicestudios.podomatic.com/entry/2012-06-24T23_00_00-07_00 
For Podiobooks, just go to podiobooks.com and try everything for free, toss a donation to the ones you like afterwards. I recommend starting with Nathan Lowell's
Quarter Share and working your way through that series, and then I can recommend you a ton of other stuff, or you can nudge EvoTerra and see what he recommends, or you can just seek out the fun like I do.
There is so much AWESOME audio out there for free!
The others are right, it's not that the kinds of stories you seek
can't be told in short form, it's just that they usually
aren't. Plus, consider that it's true of any genre -- of any media, really -- that consciously or unconsciously authors' subjects and choice of subgenres tend to move in waves. Over the last two years, we've had a number of stories that contained homosexual issues to varying degrees. It's not that EP made it part of the mission to spray us all in Liberal urine (though you may think so from the reactions even the lightest mentions get), it's that it's an issue very much in the public mind at the moment and it has filtered into our art and a higher percentage of usable submissions have had those mentions recently. I don't mention this to incite political debate, it's all really just to say that things move in waves and cycles, and the subgenre you fancy will quite likely return to vogue in the future.
*NOTE: Bill Hollweg is a HUGE fan of old time radio [OTR] dramas. If you want, I can refer you to him and he will send you with links to more Outer Limits, Twilight Zone, and other great pulp and classic stuff you've never heard of than there are hours in a lifetime to listen to.