A quick-ish question: I'm using a Spark Fun Nokia 6610 breakout board, with an on-board RGB LED. The schematic shows that the LED is connected with 330 Ohm series resistors, but has a common cathode, and thus will require active low to turn on. Is it possible to use the mbed's PWMs to control this LED safely? Is it safe for them to sink current instead of sourcing it?

when in doubt use an external (switching) transistor or better a small FET (BS170 or such)

In short yes, normally micros can sink about 10X the current they can source!

I've connected it up, and it's working perfectly well. There is less than 10mA of current for each channel of the RGB LED. Thanks for your time!

The datasheet and informationpage contradict eachother on this unfortunately:

Info page:

Digital IO pins are 3.3v, 40mA each, 400mA max total

Datasheet:

Normal current 4 mA source, -4 mA sink

Short circuit 50 mA source, -50 mA sink