keychain-manager
A key system based around accounts that each have hierarchical deterministic (HD) keychains with ECDSA public/private keypairs (the ones Bitcoin uses).
coinpayments
CoinPayments is a cloud wallet solution that offers an easy way to integrate a checkout system for numerous cryptocurrencies. Coinpayments now also offers coin conversion via Shapeshift.io.
elliptic-keychain
Library for creating elliptic curve keypairs and deriving child keys