Things I want to keep track of:
My SpaceNavigator (SN) is the Personal Edition (PE), USB ID: 046D:C626 (PE/SE are identical, just license that changes).
udev rule to automatically set up:
/dev/input/spacenavigator symlink to proper event[0-9]* device:
KERNEL=="event[0-9]*", SYSFS{idVendor}=="046d", SYSFS{idProduct}=="c626", SYMLINK+="input/spacenavigator", MODE="0666"
Single line, placed in /etc/udev/rules.d/99-SpaceNavigator.rules (for instance, the name can vary, as can the leading number, I just stuck it at '99-' since it would get read after everything else, and hopefully wouldn't mess anything up. It hasn't)
The above line is tailored to the SN-PE... note the 'c626' ProductID. Replace that with the proper ProductID if you don't have the SN-PE model. (y'know, like the super-whamma-dyne neato models with many buttons and LCD's and stuff)