Chamonix
Chamonix is one of my favourite areas for speedflying. It is where I began flying, after a couple of flights in the UK. Living in Chamonix, I was able to exceed 1000 flights per year very easily.
The valley tends to be very flyable.
Summer season
Le Tour
Le Tour lift will likely open around 8th June, this makes the hike for Glacier du Tour line very easy (1h rather than 2h).
Speed-soaring is possible at Le Tour, and I do it a lot. Lamina valley breeze of 45kmh from July, peaking around 64kmh mean for 1/2 weeks in August. The lift normally closes around 8th September.
Brevent & Plan Praz
Brevent & Plan Praz will likely open around 15th June. This is good for laps, although not the most beautiful. You can also hike from Brevent summit to access other lines.
Plan de L’Aiguille
There are some really good lines from Plan de L’Aiguille that are closed during July and August. Normally you can do 6 per day there, but sometimes there is a queue for the lift.