The CERN Hostel on the Meyrin has rooms on the CERN site. Please remember to look at the Booking Rules - CERN Hotel Terms and Conditions of Reservation | SCE before contacting them. Please use the following webform to make your reservation. In the webform the hostel management will ask you who your guarantor is, please use Kristina Gunne (email@example.com) and tick "official visitor" at the question of your status.
If you decide to stay outside of CERN, we suggest you to pick a hotel close to the tram line nr 18 ( direction CERN) which stops outside the CERN reception (building 33) http://home.web.cern.ch/directions.
We can recommend a few hotels on the Swiss side, close to the railway station where tram 18 leaves from:
or closer to CERN and the airport, but still close to tram nr 18:
Overview (marriott.com) Geneva Marriott Hotel (Completely new)
The Cointrin airport is a taxi journey from CERN (around 35 CHF) and the cost of a tram ticket is ca 35 CHF.