NOTE: As of 2015, I no longer use or recommend this method. Instead I use Vagrant to setup virtual machines for dev and testing. It’s free, relatively easy, and allows better matching of the production environment. It completely separates the development environment and you can make as many as you need. Highly recommended. I’m leaving the original answer below for posterity’s sake.
I found an answer here on the Apple forums.
In order to reclaim the /home directory, edit the /etc/auto_master file and comment out (or remove) the line with /home in it. You’ll need to reboot after this for the change to take effect (or, per nilbus’ comment, try running sudo automount -vc). This works with Mac OS X 10.5 (Leopard). Your millage may vary for different versions, but it should be similar.
As noted on that forum post, you should also be aware that Time Machine automatically excludes the /home directory and does not back it up.
One note of warning, make sure to back up your /home directory manually before doing a system update. I believe one of the updates I did (from 10.6 to 10.7 for example) wiped out what I has stored in /home without warning. I’m not 100% sure that’s what happened, but it’s something to be on the lookout for.