Hmmm... Just about anything in the BC Kootenays!
But you didn't say anything about that...
In Montana, the Going to the Sun Hwy thru Glacier NP is beautiful, but not really a road you can make any time on due to low speed limits and high tourist traffic, but if you haven't been, it's worth consideration.
US Hwy 12 over Lolo Pass between Lewiston, ID & the Montana border... home of this famous sign:
And if you take 12 over that route, the Old Spiral Hwy on the north side of Lewiston (the old US 95 route), is another great road to ride!
I don't know much about the off-raod opportunites in MT or E. WA, but in Central WA, there's a huge ORV network that's bordered by I-90 on the north and SR 410 on the south, just a little east of Ellensburg/Yakima. There's one trail, the Naches Trail, that will take you over the Cascade Crest and follows the original pioneer trail that brought settlers into the Puget Sound region. Trail maps can be purchased from the Forest Service at ranger stations in the area, or
on-line here.You can also print some of them yourself from here:
http://www.fs.fed.us/r6/wenatchee/cle-elum-orv/orv-maps.html(This ^^^ is only the Cle Elum District, there's more trails in the Naches District, but they don't have an on-line version.)
FYI - US Forest Service and WA state lands require vehicles be street legal if they are operated on forest ROADS. If operated on trails only, the machine must have an ORV permit on display. They do honor permits from other states, but I don't know about other countries.
We are planning a PNW get-together starting Aug 15th...
http://forums.banditalley.net/index.php?topic=10769.0