#1: Listen in your car
While we New Yorkers may not have our own cars, this is still a #1 pick. Think of all the times you rent a car on a vacation or business trip, or while driving to your weekend getaway. Its an FM modulator - which only means that you are creating a little FM station of your own. Not perfect sound quality, but currently the best (and most flexible option, though it doesn't work with the iPod Shuffle).
#2: Listen in your home
This is the only cable you need to plug your iPod right into 90% of the stereo equipment out there. Works with fancy stereos, cheap bookshelf systems, you name it. Why deal with stacks of CDs when you've already digitized your music. Want to get fancy? Use this to hook your computer directly into your stereo and control everything via iTunes.
#3: Listen on the road
Ok, while not "on the road" but rather in hotel rooms, the beach, or anyplace you want to share the music with friends without hooking into a stereo. This lightweight, folding speaker system plays and charges at the same time. Solid sound quality, which will make that sterile hotel room a little more comfortable on your next trip.
#4: Listen with a friend
This gadget lets you and your sweetheart share the same tunes. Share your musical universe - just add another pair of headphones. Also works for sharing movies on portable DVD players or computers.
#5: Save those photos
Although this only works with the big Pods (30gb and 60gb), its still one of my favorites. This connects your digital camera into your iPod and saves all your photos onto the internal hard drive. Reformat your memory card and start shooting again. No more need to bring multiple memory cards and you can view the pictures on the Pod's screen as well.
Are you wondering why there aren't any cases? Cases are a very personal thing - what works for you may not work for another. Same goes for headphones, but you definitely should be in the market for both.