There's the famous Doolittle house just south of there:smile:...but I digress! A couple of thoughts for you:
1. Head out River Road to Guerneville. Stop at the Armstrong Woods and take a hike through the redwoods. On the way back, do a little sparkling wine tasting in the Russion River region, have lunch at Korblel, etc.
2. Head the other direction to Annadel State park. More great trails for hiking.
3. Pacific Air Museum at STS (can't vouch for it, haven't been there)
4. The square in downtown Healdsburg is very nice
5. For a bigger drive, start with #1 and then head south on the bohemian hwy through Occidental (a really neat little town tucked away in the redwoods on the top of a hill) and down to Firestone (another neat little town), head back through Sebastopol.
6. For an even bigger drive, go all the way to Jenner on River Rd then head south on 1 through Bodega Bay and Tomales. Consider continuing all the way through Marshall to Pt Reyes. A lot of neat coastal towns.