In January of 2007 I got a Garmin GPS, and soon after that I discovered the OpenStreetMap
project. I started contributing to the project by mapping the Chicago area, where I lived at the time, and at one time I had some Garmin map images based on Openstreetmap data available here. Eventually the TIGER data set enormously expanded the coverage of the US and other sites started producing better Garmin images, but I've continued adding details to the various places I have lived and have traveled.
Some areas I've contributed to include:
If you're still looking for Garmin maps, the best ones I've found so far are from osmmaps.com