I feel like I've been talking about this forever (actually, take a look at this post from 2008 - Shifting Paradigms) but there are still some endurance athletes that look at me like a weirdo when I suggest they spend time in the gym lifting heavy (bodyweight circuits in the winter doesn't count!).
Just in case you're in doubt or you have coaches and athletes that can't see the importance of lifting for endurance athletes, take a read of this review.