Class for DHT11, DHT21 and DHT22 (temperature & humidity)

I wanted to ask you a question if I may -

you may,

I tried supplying it with different voltages (3V, 3.3V, 5V - using the
Arduino Uno's 3V,5V and the Arduino Fio's 3.3V power supply)
and for each voltage there are different readings for the temperature and humidity (a
very big difference between 3V and 5V).
what is the correct voltage that it should be supplied with?Ac

As you say according to the datasheet, any voltage between 3 and 5.5V should work. I only can confirm that the readings makes good sense at 5Volt.

(or is there a way to work around this?)

External powersupply for the sensor? does also make sense if the sensor is a bit further away, long wires.

If you use 3.5 volt and you take longer delays between the readings, does the accuracy of the reading increase?