Spotted this announcement a few days ago:
"1-watt DC/DCs extend design options"
...referring to this set of devices:
The single-output regulated devices look most intriguing:
At the top of that page, try playing around with the
Parametric Search to find the right module for your application.
Select 3.3V output voltage (what the Gumstix needs), 0-5W power, and
your input voltage (range) of interest and see what it returns.
If you don't know what to do, do something.