http://www.pro-velo-lausanne.ch/association/prestations/foires-aux-velos/

Each year there are over 60 local bike markets where people can buy and sell inexpensive used bicycles, trailers and accessories of good quality. Bicycle sales are listed here but there are also sales in other cantons.  Check out the Bourse aux vélos, PRO VELO website for further details at www.pro-velo.ch. This is a great place to sell or buy a bike.

They also have a repair center if you just need yours fixed. Sign-up is usually betweend 9h-10h, sale from 10h-12h, then pick-up of unsold bikes and your money (minus 20%) until 13h. Check website for exact times for each sale.