gpsfiledepot.com for good FREE garmin compatible maps.....
...as Shane4x4 noted.
I've used the CA topo and OSM and they're OK, not great. The Garmin 24k is better in some areas for non vehicular use. And as I noted, not routable. The southern California ones by California Trail Map look really good too, but that's just there.
http://www.californiatrailmap.com/MapComparison.aspx The map files are pretty huge, though. Usable on my Samsung Tab with the SD card, and on my Oregon 600, but not as much on my iPhone.
I tried some of the Garmin Birdseye topos, and they are definitely meh; apparently USGS topos many of which are very out of date (old maps can be super useful though, depending on what you're doing, and for offroad stuff where not much changes). The Birdseye satellite overlays are pretty good; they come from a company that claims my local areas are less than a year old, but Garmin's servers don't appear to be that up-to-date, but still not bad. I've seen some examples where they best Google's imagery though. And downloading is a chore since it only does relatively small areas. OK for hiking, but a no-go if you'll be driving over large areas, or need to download on the go (using Gaia for this is much more efficient).
I'm coming to the conclusion that using raster for smartphones, vector for handheld GPS is the way to go, since that plays to the strength of each. And I am finding that more and more of the user-made maps are nice; not just gpsfiledepot, but ones you can make through DIY Map GPS app or Mobile Atlas Creator. Can't seem to use these easily with Gaia GPS though; need to convert unless things have changed recently.
