Few weeks ago I decided to spend a weekend to try to understand Ethereum. I found the whitepaper to be pretty instructive (it even helped me cement my understanding of bitcoin). Here is an annotated version of the whitepaper by vitalik: http://fermatslibrary.com/s/ethereum-a-next-generation-smart...
Protocols and decentralized applications around decentralized file storage, decentralized computation and decentralized prediction markets, among dozens of other such concepts, have the potential to substantially increase the efficiency of the computational industry, and provide a massive boost to other peer-to-peer protocols by adding for the first time an economic layer