as a peak to bag Mont Buet is probably your best bet on the chamonix side. one of the best views in the area but a tough day out. it should be almost completely snow free in august,there'd probably be a patch at the summit but it's doable in less than a day from a refuge or camp. you can use the planpraz/brevent or flegere cable cars to get a head start on a walk to Lac Blanc and around buet. the scenery doesn't vary greatly en route because the mountains on the other side of the valley are so dominating. if you descend to the east of Buet over the swiss border above the lac d'emosson you can catch rare views of a good chunk of the pennine alps.
an interesting and quieter walk on the other side is from val ferret (champex has a small cable car) over the col du ferret and then on to peuterey. it's not as easy logistically as going from chamonix though. Mont Favre is easy and gives great views of Peuterey and Brouillard.