Insight
insight is an open-source Bitcoin blockchain explorer with complete REST and websocket APIs that can be used for writing web wallets and other apps that need more advanced blockchain queries than provided by bitcoind RPC. It is supported by Bitpay and uses their bitcore implementation.
Current live installs can be found at: https://insight.bitpay.com/, http://chain.localbitcoins.com/ and http://search.bitaccess.ca/.