Welcome to Lausanne...
I might be able to help you out here:
Primary sources should be:
Anibis.ch or
Petitesannonces.ch
For actual shops:
http://www.labonnecombine.ch/occasions/ which is in Malley, it sells used irons, stoves, TV's, vacume cleaners and other petit et gros électroménager.
http://www.troc.com/fr/ sells used furniture, it is outside town but the largest second hand place you will find.
There is a Cash Converters (rue Mauborget 12, 1003 Lausanne) close to Bel Air which sells all kinds of stuff.
There is a Armée du Salut on rue de la Borde 24 (entrance next to the Coop)
Gloryland (bad name of a second hand shop) rue de la Mouline 8, 1022 Chavannes-près-Renens
http://www.gloryland.ch...
But be aware that the offers you will get are not that great, often you will be cheaper off by buying some things at places like Conforama.