About three weeks ago, a guy accidentally shot and killed his son at a plinking place on USFS land. On September 11th, the morning edition of the Seattle Times had a map to this spot on their front page, calling it "legal but a menace".
There were two later editions of the paper published. I don't know if they have the map or not.
There's also a gravel pit up near Marysville, somewhere. I've heard that gang types like to go there to shoot, and that it is unsafe as a result -- both because they act like idiots and because, unless you're there with a group, you might get robbed. Note that I've heard that from people at the range, not from soccer moms, so I don't discount it much.
As far as good ranges, it depends on your definition of "good". Kenmore Range, [url]http://www.kenmorerange.com/[/url] has a nice facility but the people there are a bunch of control freaks. Everything which is not compulsory is forbidden. Snoqualmie Valley Rifle Range (just down the road from Snoqalmie Falls) is much freer, but is a much less-developed facility.