Know of a website where I can post (publish?) an original song - so that someone might notice it - or in the very least for friends to have access to it online?

YouTube?

I always just do it on youtube. I use iMovie to put the song to an unmoving background (either a picture or the song’s title or something).

You could do it on MySpace as well.

I think you can here.

I’ve posted a couple of short stories there and it seems to be a pretty good site.

mp3.com
I don’t know if they still do but they used to allow uploads so that artists could share their music with people to download for free.

If you just need a place to host it so you can show other people I can do that. I already made a placeholder.

www.purevolume.com

If you plan on making more use myspace.

www.reverbnation.com is an amazing site with tons of extras.
hugs xx

ilike.com
thesixtyone.com
last.fm.com