It may seem obvious for some of you, but I have decided to provide here a quick and simple tip: how to use your iPod as a portable hard drive.
Usually we interact with iPod using iTunes. That is all related to sound and video. But, if you check My Computer folder, you can see that the iPod is recognized by Windows as a USB storage device. Double click on this icon and open it. Depending on version of your iPod, you will see different folders. DO NOT TOUCH them! Instead create another new folder, I call mine "Transfer". And that is all. Now you can save anything you want in this special folder: documents, applications, zipped files etc.
Of course, this storage folder will consume some space from the total capacity of you iPod. Don't be surprised if all of a sudden there is no place to put music or video. Just check the special folder and clean it up.