I'm trying to do some research about different ways of playing videos with flash, and I can't find good answers anywhere

Is it possible to load movie files of extensions other than flv to a flash video player? I don't mean embedded swf's, just plain old .mov or .wmv or .avi or something similar..

Do sites like youtube and google video load raw movie files or do they have converted to flv's automatically? If they do, how do you suppose that's done?