Actually I am using this idea for my all of blogs based on WordPress. I was posting it manually but finally I decided to do it automatically. The idea was taken from TechCrucnh that used a wordpress plugin to auto post TechCrucnh posts. And I don’t thing there is wrong anything with automated tweets if that is a blog post.
You can download and install WordTwit plugin. This plugin will do the great job for you.
This plugin keeps track of when you publish a new post and automatically informs all followers by tweeting about it.
After installing and activating this plugin you will see WordTwit in settings menu just click on that. Now you can choose your favorite URL shortner and you have to authorize this plugin to work with your Twitter account. As you can see in screen shot I have already autorized my account and edited tweet message setting by default to “[title] – [link]”. There are some advance options that you can set and when you are done click “Update Options” button below side.