Eric has a nice website there, except that he needs to expand his horizons a bit... Nothing east of the Cascades, for peets sake! Oh well.
You've gotten some good gouge on eastern WA roads here, and we hope to see you over our way sometime. I'm looking forward to the end of this weekend, when most of the family trips will be curtailed by the start of school... getting rid of the campers, trailers, etc. is a GOOD thing for twisty road enjoyment!
The Mullan Road post is a good one. As a matter of fact, nearly any of the roads which intersect the route shown on the map will provide miles of smiles as well. There is an almost infinite variety of routes down in the Palouse that will whet your motorcycle Jones!
I take back roads south out of Spokane down to Colfax - SR 27 is giggles, then SR 26 west to Dusty, SR 127 south through Central Ferry where you cross the Snake River, and down to US 12. From there, the choices are ALL good for a nice day ride.
For those heading down south into Oregon/CA, I have developed a strong liking for US 395 south out of Pendleton. Starting about Pilot Rock, the terrain gets out of the valley floor and crosses a number of ridges that provide some nice sweepers down toward John Day. Just watch for the local LE in the Pilot Rock area... they are rather serious about the local speed limits through town!
We are truly blessed to live in a state which has so many good roads, which for the most part are well maintained.