iLibs allows you to manage multiple iTunes libraries comfortably.

You can, for example, create a Jazz library plus a Rock library and synchronize your iPod with one of them according to your mood of the day.

If there are several iPods but only one computer in the household, iLibs lets you manage each person's libraries without messing up the ones of the others. iLibs features multiple users, multiple libraries and multiple iPods support with a dummy-proof interface!