If you need to get iPod music, videos and other files back to iTunes library, keep in mind that as long as all files are still on your iPod, you can get them back to your iTunes easily. The following are feasible ways:

One of the easiest ways is to use iPod to help transfer. And transfer method varies according to different situations:

1) If all your songs were purchased from iTunes store, when you plug your iPod into your computer, it will ask you if you want to "Transfer Purchases". Click that option and it transfers all files from your iPod back to your iTunes library perfectly. See
Note this option only works for those songs that were purchased from iTunes store.

2) If some of your songs were from other souces, like CDs or from friends etc, you will need to use some iPod transfer program to help you transfer all. This is how I did. I used this iPod to PC transfer program on this. The whole process goes as follows:

Firstly Free Download this program and install it on your computer. When you plug your iPod to the computer, this program will instantly display all songs and videos on your iPod. You simply select what you wish to transfer and click "Copy" button. Done. All your selected files will be copied to your computer completely and safely.

More importantly, this won't overwrite any original files on your iPod. And all song names are preserved.

Now you can easily add those songs and videos to your iTunes library.
Simply:
Run iTunes, click "File", click "Add Files to Library..." or "Add Folder to Library..." , select the songs in the computer folder you have transferred files to. Or simply run iTunes, Drag your files in the folder to your iTunes music Library.

Here is step-by-step guide on how to transfer music/videos from iPod to computer and iTunes

3) Use this iPod to iTunes direct transfer software to help you copy all iPod files (both purchased and non-purchased) back to iTunes library.

Free Download to try now.

Many of my friends recommended it to me when I needed to transfer all my songs, videos, playlists, photos podcasts etc. from my iPod to my iTunes.
Compared with the above iPod to PC transfer software, this iPod to iTunes direct transfer can transfer more files, including music, videos, playlists, photos, podcasts, TV Shows and more.

Besides, this iPod to iTunes direct transfer software has been widely used as an iTunes alternative because some iPod users don't want to use iTunes to manage their iPod files.

Lastly, you can also burn the iTunes files into disc for backup before the files got deleted from your computer. This works only if your iTunes library is not too large.

Hope these can be helpful to you.