You can copy files from you iPod to your computer without any special software. The files are stored in hidden folders beginning with the letter F followed by a two digit number. On my computer running Mac OS X they are located here:
Just navigate to the folder containing a song you want to transfer back to your computer and then drag that song to your hard drive.
I will be writing a longer article about how to move all your songs at once and how to find a file even when it has a cryptic four letter file name like XTYW.mp3.