Bitcoin
Utilities
Pycoin
https://github.com/richardkiss/pycoin
bx
https://github.com/libbitcoin/libbitcoin-explorer
txwatcher
https://github.com/tsileo/txwatcher
hellobitcoin
https://github.com/prettymuchbryce/hellobitcoin
Mining visualization
http://www.yogh.io/#mine:last
Blockchain API and Web services
block.io
block.io
BlockCypher
https://www.blockcypher.com/
Gem.co
https://gem.co/
Insight
https://insight.is/
Chain.com
https://chain.com/
Smartbit
https://www.smartbit.com.au/
Wallets API
BitGo
https://www.bitgo.com/api/
Coinbase
https://developers.coinbase.com/
Blockchain.info
https://blockchain.info/api
BIP32
http://bip32.org/
Open Source Wallets
CoPay by BitPay
https://copay.io
Coinb.in
https://coinb.in/
Electrum
https://electrum.org/#home
Blockchain Explorers
Chain.so
https://chain.so/
Blockchain.info
https://blockchain.info/
BlockTrail
https://www.blocktrail.com/BTC
Blockr
https://blockr.io/
Bitcoin Transaction Explorer
https://github.com/JornC/bitcoin-transaction-explorer
Blockexplorer.com
https://github.com/bitcoin-blockexplorer/old-blockexplorer-php
Smartbit
https://www.smartbit.com.au/
JavaScript Libraries
Awesome CryptoCoinJS
https://github.com/cryptocoinjs/awesome-cryptocoinjs
Bitcore Library
https://github.com/bitpay/bitcore-lib
Bitcoinjs-lib
https://github.com/bitcoinjs/bitcoinjs-lib
Cryptocoin
https://github.com/cryptocoinjs/cryptocoin
BlockTrail SDK NodeJS
https://github.com/blocktrail/blocktrail-sdk-nodejs
bcoin
https://github.com/bcoin-org/bcoin
PHP Libraries
PHP-OP_RETURN
https://github.com/coinspark/php-OP_RETURN
BlockTrail PHP SDK
https://github.com/blocktrail/blocktrail-sdk-php
Ruby Libraries
Bitcoin-ruby
https://github.com/lian/bitcoin-ruby
Python Libraries
BlockTrail SDK Python
https://github.com/blocktrail/blocktrail-sdk-python
btctxstore
https://github.com/F483/btctxstore
pybitcointools
https://github.com/vbuterin/pybitcointools
Java Libraries
BitcoinJ
https://bitcoinj.github.io/
XChange
https://github.com/timmolter/XChange
.Net Libraries
NBitcoin
https://github.com/MetacoSA/NBitcoin
BitcoinLib
https://github.com/GeorgeKimionis/BitcoinLib
QBitNinja
https://github.com/MetacoSA/QBitNinja
Playgrounds
Script Playground
http://www.crmarsh.com/script-playground/
Debug Script Execution
https://webbtc.com/script
Bitcore Playground
https://bitcore.io/playground/
blockchain-demo
https://github.com/anders94/blockchain-demo/
Mnemonic Code generator
https://iancoleman.github.io/bip39/
Blockchain dump
BitcoinDatabaseGenerator
https://github.com/ladimolnar/BitcoinDatabaseGenerator
Blockparser+SQL
https://github.com/mcdee/blockparser
BitcoinABE
https://github.com/bitcoin-abe/bitcoin-abe
NBitcoin.Indexer
https://github.com/MetacoSA/NBitcoin.Indexer
Full nodes
Bitcoin-ruby-node
https://github.com/mhanne/bitcoin-ruby-node
Toshi by Coinbase
https://developers.coinbase.com/blog/2016/10/31/sunsetting-toshi
Fullnode
https://github.com/ryanxcharles/yours-bitcoin
Insight API
https://github.com/bitpay/insight-api
Bitcoind.JS
https://github.com/bitpay/bitcoind.js
Bitcore
https://github.com/bitpay/bitcore
Read
Mastering Bitcoin
https://github.com/bitcoinbook/bitcoinbook
Bitcoin Stackexchange
https://bitcoin.stackexchange.com/
Elliptic Curve Cryptography A Gentle Introduction
http://andrea.corbellini.name/2015/05/17/elliptic-curve-cryptography-a-gentle-introduction/
https://www.reddit.com/r/bitcoin_uncensored/ https://www.reddit.com/r/Bitcoin/ https://www.reddit.com/r/btc/