After battling with all the FAQ and wikis getting FastCGI to work with Apache, I found the last problem. FastCGI spawns temporary files in your /etc/httpd/log/fastcgi/dynamic directory (unless you override this in your http.conf file).
I was still getting these errors:
[Mon Mar 13 17:03:08 2006] [crit] (13)Permission denied: FastCGI: can't create (dynamic) server "/var/www/html/test.rails
/public/dispatch.fcgi": bind() failed [/tmp/fastcgi/dynamic/a452aa13f eeda365028a2d43d1b2ce13]
It turned out that my problem was SELinux getting in the way. It really locks down what the apache user can do (which is probably a really good thing). However, for fastcgi it was locked down a little too much. I intend to now fight a little with SELinux to see if I can get it to play nice.
If you want to temporarily disable it, you can run this command:
echo "0" >/selinux/enforce
you can echo a "1" to turn it back on.