Chain

Block Chain API for Developers
Link: 
https://chain.com/
Tags: 
blockchain explorers
APIs

Similar Links

Block inspector / API

Documentation for the Block inspector blockchain and transaction API.
http://blockr.io/documentation/api

Bitcoin Charts API

Bitcoincharts provides a simple API to most of its data. You can use this API to include markets data in your websites, mobile apps or desktop applets.
http://bitcoincharts.com/about/markets-api/

BTCLook

A way to verify bitcoin transactions and trace events in the public bitcoin and testnet block chain.
http://btclook.com/

Bitcoin Block Reward Halving Countdown

Bitcoin block reward halving countdown. The Bitcoin block mining reward halves every 210,000 blocks
http://www.bitcoinblockhalf.com/