Useful info

The power rating of the pins

The following is from here. However, as the person who posted the information pointed out, there appears to be no official documentation on the matter.

First we need to make the distinction between the actual GPIO pins, the ones with input/output capability, and the other pins on the GPIO header, which are ground (GND), 3V3 power and 5V power.

From the information I gathered while researching this, the GPIO total output current limit is 100mA for the newer models (40 pin) and 50mA for the older models (26 pin), with a limit of 16mA per GPIO pin (which is the limit of the board traces).

The 5V power pins can go higher. Not sure what the 5V power limit is, but I have run fans that pull over 300mA 24/7 for days without any problems (I expect the 5V limit is whatever the board traces can handle, but have I no idea what that is). The 3V3 power pins are limited by the 3V3 regulator, which is also different between the older and newer models (linear vs switching).

I have seen a few references that said the newer 3V3 switching regulator is 1A, but do note that the SoC and GPIO uses a significant portion of the available 3V3 power, so there's not a lot of power available on the 3V3 power pins.