I searched and found this for you.
There are lots of podcasts hosted here, as you can see from surfing the podcast tag or category. You can set it up this way for free by:
1) finding an external host for your mp3 files that allows hotlinking, like Fileden. Then use that link in the blog to provide a download and also to use for the Audio Player below
2) use the WP Audio Player http://en.support.wordpress.com/audio/
3) just write up your notes and put them all in the post with the above.
You can do this more easily if expensively by purchasing the Space Upgrade; then you can host the files right here at WordPress.com and upload them just like you would a picture. http://en.forums.wordpress.com/topic/wordpresscom-to-podcast?replies=2#post-660283
We provide support only for free hosted WordPress.com blogs on this forum. If you need support for your WordPress.org install then you will have to get it from here http://wordpress.org/support/ as the two run on different software.