Yes, among the 15,000+ apps in the App Store, there are several file transfer apps available, but having spent some time with File Magic from SplashData, available here in the App Store for $4.99, I can report that it's easy to use and increases the functionality of your iPhone or iPod Touch. By downloading the FREE desktop app at splashdata.com, you can transfer a myriad of file types from your desktop to your iPhone.
Why is this useful? If you are at work and want to take some files home with you or on the road to view and read, just use the handy desktop app to wirelessly transfer the files to your iPhone or iPod Touch, where they are automatically categorized. Transferring the files couldn't be easier - just use the drag-and-drop interface on the File Magic Desktop app and the files will "magically" appear on your iPhone File Magic app via your WiFi connection.
Check out the app in the App Store to learn more about it's features. Whether it's a matter of taking files with you to review on the road, using your iPhone or iPod Touch to move files from office to home, or even using the app to backup important documents, File Magic handles it well.