If you travel often and have a laptop, there is no reason to not have a cable that charges your phone via USB. Road warriors often hit the streets with more than a handful of gadgets (Laptop, music player, phone, digital camera, etc), which makes packing all the right chargers nearly a part-time job. We recommend Zip-Linq USB phone chargers since they fit in a nice small package thanks to the retractable cord. Zip-Linq throws in adapters for most of the big brands (check compatibility on their site first) so the same cable will work for multiple phones. Just toss it in the laptop bag and forget about it until your phone starts asking for juice.
Look for it online or at Wal-Mart for around $20.