If you have any money left over after buying an iPhone or iPod Touch, consider adding power by buying a few applications. Paid apps allow you to share files and sync memos with your desktop, read RSS feeds locally, keep track of tasks, turbo-charge your Twitter experience, and more.

Don't feel like spending any more money? Visit our suggestions for free apps for the iPhone or Touch.

Air Sharing lets you share files between an iPhone or iPod Touch and a Windows, Mac, or Linux desktop.
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However, if you're willing to shell out a few more dollars, you can make your iPhone or Touch do a lot more. And it's not all that expensive -- even if you buy every app in this article, you're only out about $50. That's hardly a crazy, extravagant expense -- not like buying a full tank of gas!

Read on for our list of great paid apps.

1. Air Sharing:

When your wife and your editor gang up on you, you're in trouble. Both of them repeatedly encouraged me to write about Avatron Software's Air Sharing, an application that lets you use your iPhone or Touch to copy documents from your desktop and view them when you're out and about. Air Sharing supports Microsoft Office formats, PDF files, Web pages, plain text, and movie audio and image files.

Air Sharing makes your iPhone or Touch appear to your desktop as a remote server on the network, which you can drag and drop files onto and off of. Air Sharing supports Windows, the Mac, Linux, and Web browsers.

While viewing documents in Air Sharing, you can pan and zoom with the same gestures you use in the iPhone and Touch's built-in Mobile Safari browser. You can access your files even when you're disconnected from the Internet.

The application has a couple of limitations: You can view documents, but you can't modify them. Also, to move documents between the iPhone or Touch and the desktop, both systems need to be on the same Wi-Fi network.

However, Air Sharing is great at what it does. My wife used it on our recent vacation, to bring along our travel itinerary and local information.

Air Sharing is priced at $6.99.

Download Air Sharing from the App Store.