Belkin Universal USB/VPA Charger
The other day I paid about $20 for a widget that allegedly charges my cellphone via my laptop USB port. This is part of a logical trend to using the USB port on a laptop (or a powered USB hub) as a universal slow speed charger for PDAs, iPods (mini only), digital cameras, cellphones, etc . The idea is that you carry a charger for the laptop, or you carry a powered USB hub, and no other chargers.
In practice charging the cellphone via the USB widget is very slow. I'm not sure overnight is long enough! HOWEVER, it does enable one to extend cell phone talk life while traveling. I discovered this while traveling with an almost discharged cellphone. I set my laptop power profile  appropriately and plugged the USB adapter into my cellphone. I continued to talk for another 1-2 hours. The cellphone power level stayed flat or increased slightly, so the power input was about equal to digital communications demand.
Caveat! Most cellphones were not designed to charge off a USB port. I've no idea what using one of these devices does to the cellphone LiOn battery. I suspect there's no overcharge protection, so if you left your cellphone plugged in for a few days the battery would probably be damaged. I also suspect, however, that it's probably harmless to use to power a working cellphone as described here.
Belkin sells one of these. I've seen it sold online for about $15.00:
meta: jfaughnan, jgfaughnan, charger, adaptor, adapter, power adaptor,
power adapter, converter, convertor, USB, mini-B, USB sync,
synchronization, HotSync, laptop, portability, travel, cellular,
mobile phone, sprint, Samsung, portability, efficiency, convergence,
transformer, AC/DC, wall wart
 In XP use a custom power profile for this -- never sleep but do blank screen and spin down drive -- I called my power profile "Cellphone Charger". Similar setup for OS X.