Hi Hilary,
There is a table in the database (UploadFileRestrictions) that allows you to set which file types can be uploaded to the image and document libraries.
Using this table you can then add entries to allow file types such as mp3, zip etc and even the new Office 2007 extensions - docx, xlsx etc to be uploaded to the document library.
Uploading mp3 files to the document library will then allow to create links to those files like any normal document such as doc or pdf, rather than having to embed that media file into the article which is what the Media Manager does.
In CM 5.4 we enhanced the RSS module to be able to point to a folder that contains documents in it so you can provide feeds of mp3, mov, files etc to users.
Example: http://www.website.com.au/rssdocument.aspx?folderid=1
We are also now enhancing the RSS module to be compatible with Podcasts and iTunes.\
Cheers,
David