If you are on the go a lot and want to use speakers for your iPod, instead of headphones, you will want to make sure and get the best quality sound possible. This can sometimes mean spending more money, but is well worth it in the long run if you listen to you iPod often.
The Logitech Pure-Fi Anywhere is one of the more affordable, yet great quality portable iPod speakers. Another good one is the Boston Acoustics i-DS2. Not only does this one offer a great sound quality, but it is stylish as well. The Harman Kardon Go + Play speakers combine portable speakers with a charger included so you can keep your iPod charged on the go while enjoying your favorite music or audiobooks.
JBL On Stage 200iD is another great portable speaker for your iPod. It is small, making it even more convenient to carry around than some of the larger portable speakers. If you are interested in super stylish speakers that still have a good, if not totally great sound, then the XtremeMac Tango Studio speakers are worth it to check out. The Tannoy i30 speakers are also stylish and small so they are easy to pack up and go just about anywhere you want to listen to your iPod. They are more on the expensive side, but make up for the price with the high quality sound.