Convenient to the Puget Sound-Eugene axis, Silver Lake is sited in the Mt. St. Helens National Volcanic Monument. In fact, the main MSH visitor center is on the lake, as well as a gorgeous state park, Seaquest.
We've only spent 1/2 day on the lake, but intend to go back. The eastern third is a potpourri of islets, lily marshes, channels, peninsulas, etc, just right for poking around. The other two thirds look interesting too, but we didn't have time to explore.
It's a major fishing lake, so there are some powerboats, but we saw no skiiers nor jetskis. Beautiful NW setting-mountains, trees, etc. Loaded with blue herons - there must be a rookery nearby. Good for a family group with nonpaddlers, since there are a lot of things for the landbound to do.
Several ramps at resorts and one state launch site, or even from one point off the highway.
Using the state launching ramp requires a permit ($12-13 for the season, usable at all state sites) available anywhere that sells fishing licenses.
I-5 from N or S to Castle Rock, east about 4 miles on the Mt. St. Helens Hwy.
Can't find anything in print, but there's a decent map on maptech.com