How can I activate my iPod if my PC is running Linux?
A few solutions, not all of them good:


If possible, update to iOS 5 (probably at the Apple Store) and don't use iTunes.
Find a friend with a Mac or a PC and get them to activate it.
Go to the Apple Store (as Randolph said) and ask them.
Run Windows in VirtualBox (or another VM solution), and use iTunes from there. (thanks, Fake Name)
Get sixty million of your best friends to switch to Linux and all complain at Apple for a Linux port of iTunes.
Run iTunes in Wine, if that's possible.