Since posting last night on how to synchronise Plurk and Twitter, I have come across ping.fm, a service that lets you post in one place and have your post delivered to a variety of other services, including not only Plurk and Twitter but many others too.
Go and check them out and sign up if you’re interested. They’re in closed beta so you will need a beta code to be able to register. You can use landofping.
craniac's place 
Hurray for ping.fm (and for Steve).
This is definitely a lot easier than the python script for us less techie types.