Well, the Beat influence that comes to mind first is Ginsberg's "Howl", where the influence was mainly in the long rambling lines of verse. This was considered a very Whitmanesque style and I don't think Ginsberg made any secret of this fact.
OK, I am no expert on Whitman and I am possibly ignorant here, but I never thought of Whitman and Snyder as directly related. I guess I always thought of Whitman as a very social, "urban" personality- he was all about people- where as I think of Synder as more of a solitary nature-minded poet. I guess this isn't much help. I could stand to learn a bit more about Whitman I guess.