Where are you? Elkhorn is cool. The Russian River is great if you want an extended adventure experience. You can put in at many spots between Healdsburg and Guerneville and down to the coast. Heading up from the Goat Rock area at highway 1 and River Road is fun and relaxing. Heading to Guerneville from Healdsburg is an extended trip that's a lot of fun too.
Lake Sonoma can really be cool as well if you get a campsite and stay over. Paddle to your site and enjoy the seclusion of some of the wilderness spots or stay in one of the more well-used spots. Either way, it's an enjoyable trip. Reserve spots online at Campground Details - Boat-In Sites (Lake Sonoma) (CA), CA - ReserveAmerica - [nrso]