Apple's iOS 4.2 update doesn't hit the virtual shelves until sometime in November, leaving you without wireless printing for at at least another month. Here's how you can print from your iOS device right now, no cables attached.
http://tiny.cc/iosprint
If you've been aching for wireless printing from your iOS device, you're probably already aware of printing apps like Print Central, Print, Print Bureau, and the like. They work with your computer to enabling printing of various documents. While these are all completely legitimate options, they're pretty obvious and easy to figure out on your own. Instead, let's take a look at other ways you can print from your iOS device.
Pogoplug
CloudEngine recently released a firmware update for Pogoplug that enables printing for any connected device—including iPads, iPhones, and iPod touches. What's a Pogoplug? It's a Linux-based storage appliance that's sort of a plug-and-play NAS. In addition, it shares your files on the web so you can view and add files remotely. It works by plugging in a hard drive or two, but now you can use an open USB port on the Pogoplug to connect a printer. Most HP and Epson printers made after 2005 should work, so if you've got a Pogoplug you just need the free Pogoplug app for your iOS device and you can start printing right away. [Pogoplug via iTunes App Store]
Air Sharing
Air Sharing is a great iOS app for transferring files between your computer and your device. I was surprised to find out that it actually supports wireless printer and works phenomenally well with Wi-Fi printers on your network. (Thanks iPad Today!) What's great about Air Sharing is that it just connects to the printer—there's no intermediary to worry about. You just choose a printer and it elegantly handles the job. What's also really great about Air Sharing is that it's around or less than what you'd pay for a stand-alone printing app ($3 for iPhone/iPod touch) but printing is just a bonus feature. [Air Sharing Air Sharing HD via iTunes App Store]
Not all printers have this capability, but printing via email is a new feature that's making it's way into the latest web-connected printers (especially from HP). If you don't know, check and see if your printer has an email address. If it does, you can send it supported documents and it'll print them. This is a great option because it requires no special apps and you can do it from any mobile device, iOS or otherwise.
Getting in on the Beta
Although you can update to iOS 4.2 until November, Apple recently seeded an iOS 4.2 beta to developers. If you're not a developer, you're not entirely out of luck. All you really need to do is know someone who paid the $99 fee. iOS developers can add up to 100 devices to their account, so your developer friend can register your iPhone, iPod touch, or iPad using it's Universal Unique Identifier (UUID - here's how to find it). You'll also need to update your Mac to the latest beta of Mac OS X if you want to print via printer sharing, seeing as only three printers are currently supported at the moment. Printing is also a little finicky in the beta. The disadvantage is that this method might not work so well, but if you're upgrading an iPad you get all the nice iOS features you've been longing for.