Accommodation
From Swisswiki
If you are looking for a room in an apartment (in German commonly called a WG or Wohngemeinschaft, meaning apartment-sharing community), there are several places you can look. Most of the following links lead to German websites, although advertisements can be found in English, Italian, etc.
http://www.wgzimmer.ch
Here you can place an ad(vert) to either offer or find a room, as well as search available rooms/roommates. Switzerland-wide.
http://www.wg24.ch
Similar to that above.
http://marktplatz.unizh.ch or http://martplatz.ethz.ch
These two addresses both point you to the ETH/Uni Marktplatz/Whiteboard--just check out the link for "Wohnungen." This site is also great if you're looking for used items, sports partners, etc.
Siedlungen
There are some special ecological "Siedlungen" (communities) such as http://www.kraftwerk1.ch that you might see advertised. Some offer one community meal a day, which is included in the rent.
Searching for an Appartment/House in Switzerland
There are various websites available, however some of the most popular ones are :-