Hash trees are pretty cool. For some fancier uses, see the Peer to Peer Streaming Protocol (PPSP), which is authored by the libswift/tribler guys.

https://datatracker.ietf.org/wg/ppsp/documents/

Basically, instead of the stream source having to sign every single new chunk (so peers can verify that they're getting the right data), the source signs subtree hashes of the new data and slowly builds up a larger hash tree. Once the stream is over, the complete hash tree is instantly seedable by anybody in the original stream.