I believe you can change the drive strengths of the GPIO outputs. I need to drive one LED at 16mA. However I cant find anywhere where you can do this. I am using the RPI.GPIO python module so it would be handy if this could be done in python.
GPIO source/sink current can be programmed to be 2 mA to 16 mA. The hardware default is 8 mA, but the OS may change it to something else.
For details and caveats, see: http://www.scribd.com/doc/101830961/GPIO-Pads-Control2