The Ausable river is great for anything from a day trip to multiple days. Many camping sites (some water access only) along the way. There are both private and National Forest camp sites. The National Forest sites are large with quite a bit of privacy, and very inexpensive. The ones on Cooke Pond at Sawmill Point are primitive but have well maintained brick outhouses.
The Ausable runs from Grayling to Oscoda where it flows into Lake Huron. There are six Hydro-Electric dams owned by Consumers Power along it's length. If you run the length it would be a multiple day trip with portages over these dams. The Big ponds of Cooke and Foote Dams can be like canoeing on a large lake. On a windy day they can be a challenge. On a calm day these big ponds can be a pleasure to explore.
Head upstream from Sawmill Point and you can Canoe up to the backsides of Lumbermans Monument and Iargo Springs. Both are along River Rd. which runs from M65 to US23 in Oscoda. Many camping sites in this stretch that are accessible from the river and by vehicle off River Rd. Old Orchard Park is a VERY large private camp ground if you like community camping. If you like privacy go with the National Forest sites. Sawmill point is well-spaced comunity type camping. There are also sites where you won't see your neighbors all along Cooke and Foote ponds.
One of my favorite sections of river to canoe is below Foote Dam. This is the last dam so it's clear sailing all the way to Lake Huron. This is a nice day trip. There's a launch site / parking area just below Foote Dam off Rea Rd. This section is more like canoeing a river. Many bends and some obstacles. The river is slow moving with deep holes through this stretch. Many spots to stop and have a picnic and swim.
From Foote down to Whirlpool launch site is a couple hours if you canoe. If you stop for a picnic and swim you can take as long as you like. Whirlpool launch site has parking / out houses. Down stream from Whirlpool is a nice stretch of river but as you get closer to Oscoda you start to see houses and such along the banks. There's a nice city park on the left bank just after you pass under the River Rd. bridge. This is a good spot to stage a vehicle and get out of the river. If you have only one vehicle it's simple to canoe the ponds and canoe back to where ever you left from. It's not too hard to canoe upstream to a picnic spot and then back to your vehicle. There is alot to see all along this stretch of River Rd. between M65 and US23 Oscoda. There is a daily fee/tag or annual sticker needed to park in the National Forest lots and campsites.
River Rd. Between M65 and US23, Oscoda Mi.