After using Audacity, GarageBand, or another program to record and edit an audio file, there are several ways to distribute your work. Use iTunes to share podcasts or songs with a wide audience, or embed audio directly on a webpage for those interested in the context of the work.
Apple has detailed instructions on how to set up a podcast in iTunes, beginning with setting up an RSS feed and walking through the upload process. For uploading other types of audio, GarageBand's "share" pulldown menu provides a direct export to iTunes.
For web designers, HTML5 includes an <audio> element, a method of standardizing how audio files can be embedded on a web page. Learn more from W3Schools tutorials on embedding multimedia with HTML5. Web design tools such as Dreamweaver or Wordpress also allow for audio uploading and sharing, though audio sharing necessitates a space upgrade within Wordpress.
Social audio sharing sites provide an increasingly popular forum for uploading and distributing original audio content. SoundCloud offers a way to upload music and share via popular social networks such as Twitter or Facebook, as well as within the SoundCloud system. A SoundCloud widget enables users to create their own embeddable audio player for use on websites as well.
For sending original audio files privately to specific people, consider using a cloud-based service such as Dropbox or Google Drive. With these services, control exactly which collaborators receive the files.