I received a copy of the GUIDE TO ESSENTIAL KNOWLEDGE for my birthday. It is full of all sorts of interesting stuff. Here are the languages spoken in Switzerland and the approximate percentages.
German 63.7% (official language)
French 20.4% (official language)
Italian 6.5% (official language)
Romansch 0.5% (national, but not official language)
This data is based on the 2000 census.