In the summer be sure to visit the Cirque de Fer a Cheval, a spectacular valley on the Swiss border half an hour past Samoens with glaciers, waterfalls and towering cliffs. In addition to a loop track on the valley floor there's also tracks leading higher up and a couple of refuges where you can stay overnight.
Samoens itself is also a pretty town worth having a look around and has a good lake area if Lake Montriond gets too busy. If you fancy a drink be sure to give Vin sur Vin a visit, a great little wine bar run by an Italian.
Col de Cou is awesome for views into Switzerland and not too difficult a hike. Any of the trails leading up from Vallee de la Manche are worth a go for great views and the feeling of getting away from it all.
O'Kariboo in Les Gets for the best burger in the area.
Try out either of the Golf clubs – Les Gets or Avoriaz, paddle boarding on lake Montriond is amazing, hiking anywhere on the mountains, BBQs at the lakes in Les Gets or Montriond, drinks and table tennis at bar apre'ski in Les Gets, white water rafting and canyoning with Frogs Rafting.
Mont Chery in powder or during peak times as it's generally quieter. The freeride section and beyond on Chamoissiere is usually pretty epic on powder days too. Le Grande Terche is the ultimate hidden ski resort and is rarely busy even in peak weeks.
Winter – off the piste
Ice-skating is great fun, if only to laugh at yourself falling over. Watch an ice hockey match during your stay. Take a tour round one of the Fromageries in either Les Gets or Morzine and watch how the local cheeses are hand made. Les Gorges du Pont du Diable, on the road to Thonon, is really worth a visit – think Wookey Hole but in France.