HP has announced an iPhone app that lets iPhone users print remotely to HP printers that have the ePrint facility. Printers with the ePrint facility have a direct Internet connection and their own email address. If you send email to them they will print out the body of the message and the contents of any attached files as long as those files are in common office formats.
There was already a BlackBerry app that reportedly did much the same thing.
ePrint machines intended for public use are now found in many FedEx Office stores, many Hilton hotels, some Air Canada Maple Leaf Lounges, and some print locations powered by PrinterOn.
The FedEx Office site does not mention the new iPhone app, but does mention the BlackBerry app. Its instructions for the BlackBerry likely parallel the iPhone app's, and tell you to download the app, select email with the attachment you want printed, select Print from the menu options, search for your preferred FedEx Office location, then select Print again to submit the job. You will get a confirmation email with a retrieval code. You go to the appropriate machine in the self-help section of the FedEx Office store and input your retrieval code. You can preview it before setting print options, and then you can print it. The cost varies by store, so you might want to check at the counter before proceeding.
Most PrinterOn locations are in hotels that cater to business travelers and have business centers. Typically, you enter a retrieval code, and then use it to print your document when you get there. Costs are set by the hotel but the PrinterOn service at many of the hotels whose listings I reviewed was complimentary.
Private owners of ePrint machines can set the machines to receive only from a whitelist. However, I've left mine open to the world for months, and no spam (or business documents from road warriors) has shown up yet.