What general aviation single-engine piston pressurized airplanes are there?
The ones I know of 


Mooney Mustang M22 (out of production)
Piper Mirage (they claim its the only pressurized piston single on the market)
Cessna P210N (out of production)
Lancair IV-P (falls under experimental but is in "production" none the less) 


For what its worth this is a pretty small category of plane to begin with. The M22 was not very successful (although it was ahead of its time) and there are not that many left flying (less than 20 I think). The P210N saw some better success and the Mirage seems to be selling but in the end of the day extra maintenance and complexity of the plane its self does not lend to a very practical plane considering there size and performance numbers. 

If we are talking about the less produced or experimental designs we can add, 


Junkers Ju 49 - One of the early test beds for pressurization 
Farman F.1000 - Altitude record plane 
Airco DH.9A - Another early frame used for testing