Macworld reviewed Printopia 2.1.5 an expensive ($20) but very useful utility that lets you print from your iOS device (iPad, iPhone, iPod Touch) to any printer that is connected in any way to your Mac. This is a utility for your Mac, not an iPad app.  Your Mac needs to be running Leopard (10.5.8) or Snow Leopard to run the utility.

Read more about it here.