I've just bought a Solio Classic solar charger (http://www.solio.com/charger/explore-solio/what-is-solio.html). After charging the Solio battery via USB, I've successfully used the PSP charging tip (sold separately) to charge my Zaurus C1000.
I'm now testing the use of the solar panel. According to charger and Zaurus specifications, 1 hour of full sun should give roughly 1 hour of Zaurus battery, which would be very nice :-)
The very first results are encouraging but need to be confirmed ; I'll probably be able to give more information on that in a few days !