My friend Kyle Davenport (aka Quickening) has done some pretty amazing hardware and software hackery on his sl5500. Check out his Zaurus page at
ALERT! March 4, 2011 - Kyle has taken quickening offline temporarily for an upgrade. Check back in a day or two if you need something from there and it is still not back up, or check the Wayback Machine at http://archive.org.
An annotated list of some of the many, many assorted scripts he has written for the zaurus can be found at:
And the scripts from the above list, as well as many others, are available for downloading at: