If you have more than one iPods and want each iPod have different content, the only way that I found is managing your iPod content manually:
Step 1: Run iTunes, select main menu->Edit->Preferences, switch to Device tab, check Disable automatic syncing for iPhones and iPods.

Step 2: Connect one of your iPod or iPhone to computer, select iPod or iPhone in the iTunes’s Devices list, check Manually manage music and videos and press Apply button.

Step 3: Now you can managing your iPod and iPhone content manually. For add songs, videos, and playlists from iTunes to your iPod or iPhone, just drag the item to the iPod or iPhone icon in the Devices list on the left-hand side of the iTunes Window:

Repeat step 2 and step 3 for your other iPod or iPhone.
Tags: iPod Software
http://support.apple.com/kb/HT1495?viewlocale=en_US
This is article about managing multiple ipods on one computer I use method 3 and have different library’s for each of our ipods. Just have to hold shift while opening itunes and it allows you to choose library to sync with. Hope this helps Craig