Run this file to instal 37signals' Pow but use an Apache proxy instead of the firewall rule.

install_pow_with_apache_proxy.sh

curl get.pow.cx/install.sh | sh

# We don't actually want the firewall rule that pow installs
echo "Get rid of those silly firewall rules for port 80."
ports=($(ruby -e'puts $<.read.scan(/fwd .*?,([\d]+).*?dst-port ([\d]+)/)' "/Library/LaunchDaemons/cx.pow.firewall.plist"))
HTTP_PORT=${ports[0]}
DST_PORT=${ports[1]}
RULE=$(sudo ipfw show | (grep ",$HTTP_PORT .* dst-port $DST_PORT in" || true) | cut -f 1 -d " ")
[[ -n "$RULE" ]] && sudo ipfw del "$RULE"
# Unload the firewall plist and remove it.
sudo launchctl unload "$FIREWALL_PLIST_PATH" 2>/dev/null || true
sudo rm -f "$FIREWALL_PLIST_PATH"

# set up the Apache Proxy
echo "Configure the Apache proxy."
cat <<EOT > /tmp/pow_proxy.conf
<VirtualHost *:80>
  ProxyPass / balancer://pow
  ProxyPreserveHost On

  <Proxy balancer://mongrel_cluster>
    BalancerMember http://127.0.0.1:20559
  </Proxy>

  RewriteEngine On

  # Redirect all non-static requests to cluster
  #RewriteCond %{DOCUMENT_ROOT}/%{REQUEST_FILENAME} !-f
  RewriteRule ^/(.*)$ balancer://mongrel_cluster%{REQUEST_URI} [P,QSA,L]
</VirtualHost>
EOT
sudo mv /tmp/pow_proxy.conf /private/etc/apache2/other/pow_proxy.conf
sudo chmod 644 /private/etc/apache2/other/pow_proxy.conf
echo "\n\n"
echo "################################################################################"
echo "Now just (re)start Web Sharing in OSX's Sharing Preferences and"
echo "symlink your application into ~/.pow as per the pow directions."
echo "See http://pow.cx for more information."
echo "Protip: You may need to restart your computer for the resolver to work."
echo "It's an issue with Pow itself, not my fault. :-)"