Drive an LED direct from a PIC IO pin (ie no current limiting resistor)

[mister_e]

Edit: Hmm: I'm thinking here that I'm only going to be switching 3.3V across the leds - do mosfets work ok that low? (all the ones I'm seeing on digikey are typically 20V VDS or more ...ok so that's a max figure, but never having worked with MOSFETS previously, are they ok with switching 3.3V well)

You want to look for Logic Gate one and/or with a low Vgs... at least under the battery voltage