Does Mac OS X have something like SELinux? I just spent a looooooong time trying to use Macports' Apache2 to serve documents out of my home directory.  She no work!!!11  In the absence of any meaningful log data (that I could find) to go on, I decided to just plop the whole thing into the default document root ("/opt/local/apache2/htdocs").  Voila!  Immense anger!

So, does Mac OS X have something like SELinux that might prevent Apache from doing something silly, like serve files from the place I want to serve them from?  I read a little about Mac OS X's MAC framework, but that didn't seem to be what I was looking for.

I was using virtual hosts, as initially configured by Macports.
To answer your question as stated: Yes, MAC OS X has something similar to SELinux providing mandatory access control security polices and roles. As you have discovered it's called MAC and I believe it's based on the TrustedBSD implementation of the same name.

To answer your implicit question: No. MAC should not interfere with the ability to serve documents out of your home directory. Most likely either your permissions or your virtual host configuration is incorrect.

If I remember correctly the logs should be in /var/log/apache2 or /var/log/httpd. Please edit your question to contain the relevant parts of your virtual host configuration and logs.