Give your iPod some extra juice when you're away from a charger. Amazon has this Belkin Backup Battery Pack for iPod on sale for $20. Add something small to hit the $25+ free shipping mark. Note: the vibe I got from the user reviews is that this unit works best if you fill it with better rechargable batteries.
Includes 4 AA batteries and 2 extra suction cups
Provides 15 to 20 hours of additional battery life
Indicates charge levels with 4 LEDs, secure on/off switch