If you are referring to mostly US aircraft, an excellent book on the topic is the Squadron Signal "Strangers In A Strange Land Vol II", it covers many individual aircraft as well as crews etc.
http://www.amazon.com/Stranger-Strange- ... 0897472780In a nutshell, all aircraft were impounded and sent to collection/storage facilities, including wrecked aircraft/parts. A few were used by the Swiss for testing etc. After the war many were made flyable and flown back to the UK or home and then scrapped, many were scrapped where they were. Some Mustangs iirc were sold post-war to the Swiss for use in their air arm.
Crews were interred for the duration; if you walked in to Switzerland, you were put up in better facilities and had more freedom, including being able to take university/school courses. If you flew or parachuted in it was a different ball game, but still I believe better than a typical pow camp. They got pissed if you tried to escape, and if the Germans got you outside the border you'd be shot. There were of course prisoner exchanges etc., whereby some Luftwaffe crew would get sent home and a similar number of allied crew would also be released. I think also injured crew were sometimes repatriated depending on the conditions.
Seems to be a bit different in some cases for German aircraft; I recall reading about a Me 110 that had the most current radar gear, and the Germans levered the Swiss into blowing it up so that it couldn't be examined by anyone.
At any rate, this is all from my recollection of reading the book mentioned above, it's a great read. If you read between the lines there are some interesting details, such as bombers flying in with lots of fuel and no apparent damage. No conclusions on what happened in these instances are made in the book, nor am I implying any.
cheers
greg v.