txwatcherA little Python utility that lets you monitor Bitcoin addresses through Blockchain Websocket API and perform custom callbacks.
hellobitcoin A collection of simple programs which can generate bitcoin wallets, create and sign transactions, and send transactions over the bitcoin network.
btctxstore simple library to store/retrieve information in bitcoin transactions using OP_RETURN
pybitcointools Python library for Bitcoin signatures and transactions from Vitalik Buterin. Project discontinued.
pycoin Python library for Bitcoin keys, signatures, transactions. Includes full VM implementation and tools for manipulating keys (ku) and transactions (tx).
bitcoin_tools Python library for building and analyzing transactions and scripts (both standard and custom). Comes along with a UTXO set analysis tool. Includes several examples and exhaustive documentation.
WebBTC These are postgres database dumps of the bitcoin-ruby-blockchain database generated by webbtc.com.
BitcoinDatabaseGenerator A high performance data transfer tool that can be used to copy data from Bitcoin Core blockchain files to a SQL Server database
Blockparser+SQL Fast, quick and dirty bitcoin blockchain parser
BitcoinABE Abe: block browser for Bitcoin and similar currencies
NBitcoin.Indexer Scalable and fault-tolerant block chain indexer for Azure cloud platform.