dansguardian on OSX

sudo port install dansguardian
sudo launchctl load -w /Library/LaunchDaemons/org.macports.dansguardian.plist
sudo mkdir /opt/local/var/run
sudo port install squid
sudo launchctl load -w /Library/LaunchDaemons/org.macports.Squid.plist

Once this is done, one has to force the browsers to go through Dans. For Safari, System Preferences -> Network -> Advanced -> Proxies and set localhost and port 8080 to what you want filtered:

For firefox, it's a little more complicated

1) in /Applications/Firefox.app/Contents/MacOS, create a file named firefox.cfg that contains:

//
lockPref("network.proxy.http", "127.0.0.1");
lockPref("network.proxy.http_port", 8080);
lockPref("network.proxy.ssl", "127.0.0.1");
lockPref("network.proxy.ssl_port", 8080);
lockPref("network.proxy.ftp", "127.0.0.1");
lockPref("network.proxy.ftp_port", 8080);
lockPref("network.proxy.type", 1);

2) edit /Applications/Firefox.app/Contents/MacOS/greprefs/all.js and add these two lines:

pref('general.config.obscure_value', 0);
pref('general.config.filename', 'firefox.cfg');

You'll need to check these every time you upgrade firefox...