Human Swarm & Ant Swarm
I can sit on my back step for an hour just watching ants and other bugs crawl across the vast mini-landscape. Their ability to explore & survive as a collective intelligence is one of the wonders of life. Humans are just as immersed in their own 'hive minds' whether they be political rallies, evangelical mega-churches, or the Internet.
The idea of a collective mind has also spawned alot of fictional examples; Matrix Sentinels, The Borg, Buggers, Aliens, Geonosians, and probably many others that I'm not aware of.
This National Geographic article tries to tackle the mystifying complexity of life operating in networks-