@joshgreg,
There is a plugin called “WP JV Custom Email Settings” that does what you want for posts.
Like you, I (as secretary of a club) wanted to send e-mails to members when I published minutes of our meetings. So I took this plugin and adapted it to process documents.
I have loaded this to GitHub as “WP Document Revisions Email Notice“. It still needs some work to get it properly delivered to WordPress, i.e. generate the .pot file and documenting the available filters. However it is fully functional.
This sends emails to registered users of the system. It does not support sending it to an arbitrary list of external e-mail addresses.
You can download the repository as a .zip file and use that as plugin file. Should you do this and encounter any issues, please raise them as issues on the GitHub repository rather than here please.
Hope this proves to be of use,
Neil James