The Mont Blanc Unlimited ski pass might only be the size of a credit card, but with the addition of the Evasion ski area (Megeve, Saint Gervais, Les Contamines, Combloux, St Nicolas & La Giettaz), it gives you access to a large and wonderfully varied ski area.
With the addition of the Evasion Mont Blanc ski area in the winter of 2015/16, Chamonix effectively gained 445km of pistes (take a look at the piste map), easy access to several ski touring areas and a great bad weather skiing option for when the snow or wind is too much for the higher altitude ski areas of the Chamonix valley.
The skiing in Combloux, Megeve, St Gervais, St Nicolas and La Giettaz (all of which are linked) is predominantly below the treeline and not too steep. Blue and red pistes predominate - if you like Les Houches then you'll love these areas. In contrast stand-alone ski area of Les Contamines is much more open, but still with blue and red pistes making up the majority of the skiing. Its like the Le Tour ski area but much bigger, and you get to see the other side of Mont Blanc too. If mountain side apres-ski is important to you, then you should head to the legendary Folie Douce at the top of Mont Joux in St Gervais/Megeve for afternoon DJ sessions.
Access from the Chamonix valley is quickest by car. It's about 25 minutes from Chamonix centre to the closest area, St Gervais, and about 45 minutes to the furthest away, Les Contamines. All the ski areas have large car parks at their base stations. If you'd rather take a bit more care of the environment then the train from Chamonix to Le Fayet followed by either public bus or the Tramway du Mont Blanc up to St Gervais is one option, alternatively you could always ski at Les Houches then take the Tramway du Mont Blanc down to St Gervais, and return the same way at the end of the day.