Have you considered portable speakers that are battery powered (or passive) that connect via the headphone jack or ones that connect via Bluetooth?
For example:
Headphone jack, rechargeable battery powered:
[ame]http://www.amazon.com/iHome-iHM7-Rechargeable-Speaker-Black/dp/B0023NVS3K/ref=cm_cr_pr_product_top[/ame]
Headphone jack, passive:
[ame]http://www.amazon.com/Philips-SBP1100-37-portable-speaker/dp/B000GJMUS0/ref=sr_1_23?s=electronics&ie=UTF8&qid=1282469151&sr=1-23[/ame]
Bluetooth battery powered:
[ame]http://www.amazon.com/ArtDio-2-0-Portable-Bluetooth-Speakers/dp/B0014KO7P4/ref=sr_1_16?s=electronics&ie=UTF8&qid=1282469461&sr=1-16[/ame]
Bluetooth battery powered but $$:
[ame]http://www.amazon.com/Soundmatters-foxLv2-Bluetooth-Pocket-sized-Loudspeaker/dp/B00313JD06/ref=sr_1_2?s=electronics&ie=UTF8&qid=1282469461&sr=1-2[/ame]