It depends what type of shots your looking for. I hear that IS lenses for video are pointless, but of course they'll always help in the still photo department! The same rules apply as if you were taking stills to be honest, but unlike stills you won't be using flash obviously, so your looking for a fast lens.
A 70-200 2.8 would be a good bet, and a 50mm 1.8, or a 1.4 if your budget is good.