There's tools that let you easily edit mp3 tags after exporting the file out of Audacity. I use the tag editor from
http://www.mp3tag.de/en/, which works well for me. I don't use a Mac, so I can't recommend one there, but I'm sure there's something out there.
I browse the mp3s on my player by genre, and I'm sure some other folks out there do as well, so it'd be nice to get a "podcast" genre tag in addition to the basic artist, album and title tags. Year and track are also nice to have, probably, though I don't really make use of them.