BlockTrail

Bitcoin Block Explorer is an open source web tool that allows you to view information about the blocks, addresses, and transactions created by Bitcoin.

Documentation for the Block inspector blockchain and transaction 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.

OmniExplorer is a Block Explorer for the Omni protocol which is created and maintained by the Omni Foundation. It allows you to query address balances and transaction data on the Omni protocol. Over time additional statistics, information, tools may be added to assist the community.