1) Grand Canyon National Park
Grand Canyon is about 2 - 2 1/2 hour drive from Sedona. You can easily take a day trip there. If you are looking to visit, my recommendation is to enter the park from the east entrance, stop at as many view points as you would like, stop by at the Village, then, exit out of the south entrance. You can stop at Flagstaff to grab dinner before you head back to Sedona. The most view points at the South Rim is located along the freeway 64. It is more convenient if you enter from the east entrance. Also, you can stop by at a Najavo park and spend some time shopping for hand crafted jewelries made by Navajo people.
Ideally, I would spend some time at the sunset and later to stargaze. But you won't be back in Sedona until late depending on the season. Change in colors of the canyon from yellow to orange to purple to blue are magical.
2) Jerome/Cottonwood
Jerome is an old mining town located about 30-40min south on 89A from Sedona just past Cottonwood. It is also known for haunted hotels and cool shops. Because it is located way above Cottonwood, the view from there is amazing. But the drive up there may freak some people out.
Cottonwood is a cute little town located about 20-25min south on 89A. It Kinda gives you an old western town vibe. Pizzeria Bocce is my fav pizza place in Sedona area. There are local wineries nearby you can visit. Or take a train ride at Verde Canyon Railroad. If you like history, Tuzigoot National Monument is a cool place to visit. Blazin' M Ranch may also interest you.
3) Williams/Winslow
These are two popular historic towns on Route 66 located about an hour and a half from Sedona. However, they are located completely opposite in directions from Flagstaff so don't try to visit both on the same day. If you are into Route 66 historic towns, you may not want to miss these places.
4) Petrified Forest National Park
Another national park located about 2 hours from Sedona. It is not as breathtaking as Grand Canyon but petrified trees laying on the ground that are thousands of years old create some amazing scenery. You will be driving by Winslow to get here so you can pair these places up and put them on your to-do list.
5) Grand Falls (Chocolate Falls)
This waterfall (yes, there are waterfalls in AZ) is one of its kind because, as the name says, it is chocolate colored When muddy water flows in to create this waterfall, it almost looks like smaller version of Niagara Falls but it is grand! However, it only appears when there is enough water to flow through like in the spring or after heavy rainfall. You will need an AWD to comfortably drive on unpaved roads to get there. It is located Northeast from Flagstaff near Leupp.
6) Wupatuki/Sunset Crater Volcano National Monuments
These national monuments are located side by side just over an hour from Sedona. From Flagstaff, just take 89A north until you see the sign. It is not well marked so you might want to put it in your GPS. They may not wow you like Sedona or Grand Canyon but cool places to take a side trip to.