I've heard that fish are able to swim in tight schools in part due to their lateral line. Basically this anatomical feature can sense small vibrations and therefore can aid in schooling. While sight aids in schooling, apparently a blind fish is capable of schooling with only its lateral line intact.
Starlings do some pretty crazy things, and often it looks like schooling. How do they do this without an analogous feature like a lateral line? I have no idea. Check out these crazy starlings mobbing a tree (video) in schooling form.
If you are going to only check out one link in this post it's this one of starlings. (video) Turn up the tunes or something and watch the whole thing. awesome. [I think I've seen this posted somewhere else before. Hope it wasn't bayblab.] The excuse for schooling in fish as described in the first link, namely predator evasion, simply does not apply to the nuttiness of these crazy formations.