Here are some running exercises. I believe they would benefit walkers too.
From Women's Running Magaizine 4 Glute Exercises that will make you a Stronger Runner (substitute walker).
I am an avid walker and hiker. My favorite is a long hike. I also enjoy taking off and going on a meandering walk for a few hours. I've hiked rim to rim in the Grand Canyon and I did 3 Burning Boot Walks on Vancouver Island.