Maps! Easily one of my favorite things about RVing and traveling in general is looking at maps. And as much as I want to jump right to the mapping sites it's probably a good idea to link to a few sites that explain just exactly what boondocking is. Then we'll get to the maps. :)
What is boondocking? - "Boondocking is essentially camping without hookups. You may also hear it referred to as 'dry camping'..."
Boondocking Tips - the How to and Where to - "Boondocking, Off the grid, Off the cord, Dispersed Camping, Dry Camping or Wild Camping are all names for camping or RV'ing without any hook ups (water, electric or sewer)..."
Freecampsites.net - Easily my favorite site for finding boondocking campsites. Zoom in on the map and click on an icon that looks interesting. From there you can get a lot of info on the area with a link to google maps to get directions.
Campendium - I haven't used this site much but I hear a lot of more experienced RVers do. It looks to have a combination of free camping and paid parks.
Boondockers Welcome - Also known as moochdocking. Don't let that fool you. It's a cool idea.
Public Lands Interpretive Association - A map of western states. There is a massive amount of land (mainly out west) where boondocking/free camping is allowed. BLM land, National forests, this map shows those and more.
How to Overnight at Rest Areas, Overlooks & Trailheads - A video by Robin at CreativityRV giving tips about overnighting at some places you may not of have thought of.
Tips for Free Overnight RV Parking at Walmart - Yes you can "camp" at Walmart. A video from the guys at Long Long Honeymoon.
OvernightRVParking.com - A website describing other options and rules of etiquette for overnighting at different locations. Be aware it is a paid subscription service.