What is the "blockchain"? What is the blockchain? I keep hearing about other "blockchain technologies", does this mean other cryptocurrencies or what?
The bitcoin block chain is the record of every bitcoin ever generated and every transfer of bitcoins from one party to another. Each crypto-currency that is based on the same type of technology as bitcoins has its own block chain. When people talk about other blockchains, they mean other currencies based on the same distributed currency / published transaction model (namecoin, Ixcoin, and so on).

The phrase "blockchain technology" is a reference to this model of published transactions to implement currencies with no central authority.