This video of Snow Geese (and some Ross's Geese thrown in there as well) isn't nearly as good as the million-bird video Gayle posted in the ABCs, but it's mine...
http://www.youtube.com/watch?v=0qmbsit4t0wI merged a couple of videos I shot at the Crane Festival in New Mexico last month (my first attempt at video editing). There is a nightly ritual where the Snow Geese fly in from their feeding spots to an area of shallow water where they roost at night. They have a habit of flying in when it's almost too dark to see, so the video quality isn't great (and YouTube's conversion/compression didn't help any), but the sheer numbers are fun!
In the second half you occasionally see a bigger bird among the Snow Geese; those are Sandhill Cranes, and the big gray birds in the water are also Sandhills (more video of them later, after more editing).