The only method I can find floating around on the net is to connect a capacitor and resistor in parallel across a digital pin and measure the time required for the capacitor to discharge.
Is it possible at all to do it using an analog input pin?
You can measure/calculate a resistance using an analog input. Wire your circuit up like the push button tutoria: http://www.arduino.cc/en/Tutorial/Pushbutton but replacing the pushbutton with the resistance you want to measure. This makes a voltage divider, with the voltage in between the two resistances equal to:
voltage = 5 * x / (R + x)
where R is the known (pull-up) resistor and x is the unknown resistance you're trying to measure. When you read this voltage with analogRead() you get a number between 0 and 1023, with 0 corresponding to 0 volts and 1023 corresponding to 5 volts, making the formula:
analog input = 1024 * x / (R + x)
Often, this value is all you need. If you really need to know the actual resistance, use this formula (assuming I did my math right):