Inland from Eugene are the Three Sisters, including a "glass" (obsidian) mountain (cliff). Or head north from there towards Mt. Jefferson. All great hiking country.
Thumbs up on the Rogue River - beautiful area!
Any hikes through the coast redwoods are worth it, especially if you've never been in those groves before. As far as I'm concerned, that's pretty much heaven!
As for driving home, if you take the I-5 south from Eugene, when you get to Grant's Pass (right next to the Rogue River!), take the road to to the coast. You'll go through Jedediah Smith State Park (California), with some nice redwoods, then hit the coast and go past the Redwoods national park. Don't miss those two, even if you just camp a night or two in each and day hike. Then follow the coast road on down toward Point Reyes / San Francisco.
You can go straight to the coast from Eugene, but then you'll miss Jedediah.