Okay, I'm nearly there, but haven't quite made it, yet.

Thanks for the birthday wishes, too, by the way. :]

/etc/exports now reads:
/home/matthew/public_html -maproot=root -network 192.168.1

I mount the filesystem, as root, or as matthew on the OS X machine with 
this command:

[localhost:/Users/matthew] root# mount_nfs 
sonic:/home/matthew/public_html mountpoint
[localhost:/Users/matthew] root# cd mountpoint
mountpoint: Permission denied.

As you can see, strange things are happening!

Now, even with the pubilc_html directory, public_html's contents, and 
the mountpoint directory all chmod 777-ed, I get permission denied.

Something must be wrong with that!

Any thoughts? Am I mounting it wrong? What else could be the problem?

Thanks very much!

~ Matthew