Garmin
From Jon's Wiki
Garmin GPS gadgets can be loaded up with Open Street Map data. See here for instructions. You may need to access the Garmin as a USB storage device first, so if it doesn't immediately come up, poke this in udev somewhere:
# /etc/udev/rules.d/51-garmin.rules
SYSFS{idVendor}=="091e", SYSFS{idProduct}=="0003", MODE="666"
Then grab your map from here; pick a generic routable map of wherever (pick a country, or select areas manually), and save the generic compressed image file. Unzip the gmapsupp.img file and stick it in the Garmin folder of your GPS device storage and you're done.