Hi Tarri,
Just in case you don't know about this, there is a wealth of podcasts available at SotT here: http://www.sott.net/podcasts/listall
Most of those have also been transcribed, see here: http://cassiopaea.org/forum/index.php/topic,13992.0.html
You could run those through the programs Ripred just mentioned if that makes for better understanding.
The same can be done with the Cass transcripts, to be found here: http://cassiopaea.org/forum/index.php/topic,13581.0.html
Or with the online wave series here: http://cassiopaea.org and so on. Plenty of possibilities if you are creative....
Hope this helps a bit.
Edited to add: some browsers have a plug-in available for speech audio from websites. Does the same trick as the Nuance progs.