As also replied in the 'Courchevel' post of today, this is a useful site:
http://bravomike.free.fr/fs20022.htm All with pretty short runways, though. If you need a long runway you're probably flying something that shouldn't be anywhere near the Alps anyway or you haven't found the brakes yet.
As Ozzy says, you're spoilt for choice anyway as the Alps are pretty widespread (I presume you're referring to the European ones) taking in France, Austria, Switzerland and Northern Italy for starters. So if you must have your long runway try Zurich, Geneva, Salzburg or Grenoble or Turin.