How to start/stop/restart launchd services from the command line?

How do I restart, say for example my httpd or afpd, running any Mac OS X >= 10.5 (Leopard-), without having to use the GUI and go to System Preferences -> Sharing and unchecking/checking "Web Sharing"?

I'm looking for the canonical equivalent to Debian's invoke-rc.d apache2 restart .

EDIT: The question is about launchd controlled services in general , not specifically Apache (-which was simply an example).

launchctl(8) is your friend. Just keep in mind that some of the services (sshd for example) are disabled in the configuration file so you will need to use the -w switch when loading them. Here's an example of sshd

$ sudo launchctl load -w /System/Library/LaunchDaemons/ssh.plist

You can stop the service using the unload subcommand.

$ sudo launchctl unload  /System/Library/LaunchDaemons/ssh.plist

To list the services, as you might have already guessed use the 'list' subcommand ;)