Automatic Pings

How can I set up the system to send automatic pings to other sites when I update the weblog? A site such as technorati for example.
I have tried using a my-hacks.php file as I read in the docs, but does not appear to be working.
I am using the latest version of WP. There is an option about legacy my-hacks file in the options but it won’t stay activated.
If not, which files can I whack in the code for my auto pings?
Hope I make some sense.
Andy.