The awnser isnt one you will like, it is possible to just hand it to someone and let them use the ipod as it is, you can not add songs if it has been syncronized with your computer. For them to add songs or begin to use it as if it were their own they have to basically reformat it... Itunes is more then happy to do that for you when you hook it up to a new computer. There is no way for them to be able to add songs to it from their collection... unless..

Unless you purposely set yours up like I did where you click the "I will manage my own music" this is a great option because I can now plug my Ipod into ANY computer that has Itunes and simply drag and drop ANY music onto my Ipod.

Also if you are smart enough you can pull music off the Ipod and store it on your HD...