Free: Contests & Raffles.
I'd recommend buying the TOPO cd's from REI. The set comes with all of the different discs for the different regions of the state. Makes it nice so you can print your own maps on smaller paper. Is more convenient when you are hunting an area that is right on the edges of two different green trails maps.
For public lands, you will want the DNR Public Land maps, which are available by mail order from the Department of Printing in Tumwater. Look on the DNR website and you'll find a link that will take you to the Dept. of Printing site where you can order the maps you need. They are $8 each last time I looked.The DNR site is www.dnr.wa.gov