Yachats is one of the most scenic small towns along the Oregon coast. With the ocean on one side, forested hills on the other, and a pleasant river valley, there is something here to please every visitor! 

Drive up to the top of Cape Perpetua for a fantastic view from the CCC shelter. There are some easy walking/hiking trails from the parking lot at the top, or for more serious hikers, park your car at the bottom and hike up to the top.
Stroll the historic 804 trail. This 3/4 mile footpath (wheelchair accessible) runs north along the ocean from Smelt Sands park, and leads to a six mile beach. The park is named for the smelt runs here in the summer. The 804 trail continues from the park to the south for about one mile, along the edge of the rocky coastline. "Road 804" was the original pioneer wagon road in this area.
Enjoy the Yachats State Recreation area, a small ocean park on the north side of the river. There is ample parking, restrooms, picnic tables, benches and a great view.
Visit the interesting Little Log Church. Built in the 1920's, it is now a museum. Enquire locally for opening times.
Take a relaxing drive up the Yachats River valley. Seven miles up, cross a small bridge and turn left onto North Fork Yachats River Road. Follow this graded gravel road for two miles until you reach one of only two covered bridges on the Oregon coast. Built in the 1930's, it was restored in 1989.
Yachats has several "blowholes", where the ocean blasts up through cracks in the rocks, creating a water fountain similar to a whale's blow. One is easily visible just south of the river - turn west on Yachats Ocean Road and proceed about a half mile or so. Another one is located a few miles south of town at the paved pull out along Hwy 101. Both are more dramatic during high tide.
Devil's Churn is a deep cleft in the rock a couple miles south of town. There is ample parking. The waves rush into the cleft and explode upward - very spectacular at high tide. You can stay at the top, or walk down a  footpath and steps to get even closer.
The Adobe hotel lights up the ocean at night and for photography buffs, this is a good place to take night photos at high tide.
Yachats has many interesting small stores for eclectic shopping. There are several fine arts and crafts galleries, a number of boutique gift shops, a kite shop, book store, kitchen store, and an old fashioned mercantile. There is a wine bar, cheese and cracker shop, espresso, two bakeries and several good restaurants.  Nearly everything is within easy walking distance.
For a fun day trip, drive scenic Hwy 101 south about an hour to just south of Florence, where you will find the Oregon Dunes National Recreation Area. The huge dunes stretch for nearly 50 miles south, and you can take escorted tours or rent an ATV. 
Don't hesitate to ask the locals questions - they are super helpful and happy to share their town :-)