To get started, you'll need to connect your printer to Google Cloud Print, which currently requires a Windows PC, although Google says that Mac and Linux support are coming soon. Next, you'll need a device running Android 2.1+ or iOS 3+ with which to navigate to Google Docs or Gmail. Once there, open a document and choose Print from the dropdown menu in the top right corner (in Gmail, you can also print certain e-mail attachments by clicking the Print link that appears next to them).
The feature was revealed for Google Docs two months ago, was originally announced back in April 2010, and is now finally ready for mass consumption. The question is, will you use it?