The preferred method for getting topographic maps and turn by turn directions is obviously to purchase Topos and City Navigator maps from Garmin. They are kinda pricey though so for those of you looking for a less expensive alternative, here's how you do it:
Pre-Req: Garmin's Base Camp must be installed
In your browser, navigate to GPS File Depot. Select your state if you want to narrow the results down.
Regardless of what else you select for maps, get this one first My Trails-High Quality Trail and POI Maps. I do not know whether this is still the case but I tried installing these maps before without first installing this one and it was nothing but trouble. Install this one before the rest and you should be good to go.
Living in New Hampshire, I usually also go for Northeast Topo United States Part 1 of 3 and New Hampshire Wildernesses. Depending on your location you may also find maps of snowmobile, hiking, horseback riding, or off-roading trails as well.
Next - if you would like to add turn by turn directions (text and beeps only, the Oregon 6xx does not yet do voice guidance), visit OpenStreetMap. Select "Generic Routable (testing new style)" then check in the box for Enable manual tile selection. Select your tiles by eithr click in squares or by dragging to select multiple areas at once. Enter your email address and click Build My Map.
Once it's been compiled, you will be notified and will have to download the appropriate file.
At this point you will want to insert your micro SD memory card into your GPS device if you have one.
We are about to start putting those maps onto your GPS so plug your new Oregon 600/650 into the computer using it's supplied USB plug.
in base camp, right click on your internal drive
install maps
MapInstall will open
next next next etc to install all maps
wait wait wait