Perhaps the best fly-in bargain in Southcentral Alaska is Iron Creek, better even than Sheep Creek. For $240 ($80/per person for 3 people) fly with Alaska Bush Floatplane to Rainbow Lake. This compares to $300 for Sheep Creek, and the boating is better and much longer.
Have them drop you at Wayne Ross’ cabin on the east shore and hike southeast towards Iron Creek. You want to trend as far upriver as possible on Iron Creek as there is a granite-walled canyon that you don’t want to miss and you don’t want to try to hike into. By hiking upriver you will hit Iron Creek upstream of the goods. If you hike from the north end of the lake north towards the river you will miss the best part of the canyon, but you won’t miss all the whitewater.
From the put-in, a short warm up leads straight into about 8 miles of Class 3+ turquoise blue goodness. In mid-July Iron Creek was pumping at about 1,500 cfs and was biggish and very engaging. Lots of fun and fast corners and twisty drops, somewhat reminiscent of Willow Guard Rail section at about 800 cfs.
Once the canyon opens up brace yourself for a tricky section of split channels and wood. Try to stick with the older boulder bar channels and not the straight new channels that pour off into the woods. We had 4 wood portages in here and one close call with sweepers on a blind corner. Be on your toes in here as the wood is always shifting around.
The Talkeetna is reached after about 12 miles (2-3 hrs boating). Turn left here and go 30ish miles downstream to Talkeetna. A very long day or a good overnighter.