Pololu Forum user VolAnd, writing from St. Petersburg, Russia, posted about an app that turns a Wixel into a USB SD card reader. The Wixel identifies itself as a mass storage device, and basic read/write operations are working. His goal is to create files with the Wixel that he can then read from a PC. You can read more or get the app from his forum post.
This Wixel app and many others are available in our listing of community-contributed apps on the forum.
Featured link: http://forum.pololu.com/viewtopic.php?f=2&t=7143