Arising from a debate between friends Arv K7HKL, Ian K3IMW, John VK6JY and myself, I decided to trace some I-V curves for LED's and "normal" diodes.

The chart below shows the results for the 1N4148 (small signal diode), 1N4001 (rectifier), HEF305 (a large rectifier diode), 5mm Red LED, 5mm Green LED and 10mm White LED. One can conclude from this chart that the 5mm Red and Green LED's show a reasonably friendly curve, in so far as if they are operated at a slightly wrong voltage, there should be no nasty destruction of the diode. The choice of current limiting / voltage dropping resistor becomes relatively less critical. Click here for the excel sheet containing the actual raw measurements.