On my way up to Seattle from the Bay Area, I stopped at Crater Lake National Park. Crater Lake itself is 5 miles across and almost 2000 feet deep - it's the deepest lake in the US. It's also one of the clearest, which gives it a wonderful blue appearance (due to refraction).
Though you can drive up to the lake (which is in the crater of a large volcano at the top of a mountain), I opted to hike the 5 miles up one day. The trail was lined with all sorts of wildflowers.
There are some great views of the lake from the rim of the crater.
I also drove up for sunset one day - about a half hour of daylight left.
Though there weren't any clouds in the sky, it was still a nice sunset.
From Crater Lake, I drove back up to Seattle to start looking for an apartment and job.