Steem Developer Portal

Radiator - https://github.com/inertia186/radiator
Radiator is a Ruby API client to interact with the steem blockchain.
Steem-JS - https://github.com/steemit/steem-js
Pure JavaScript Steem crypto library for node.js and browsers. Can be used to construct, sign and broadcast transactions in JavaScript.
Steem-TX-JS - https://github.com/mahdiyari/steem-tx-js
Lightweight JavaScript library for creating and signing transactions. Works with frameworks like Nativescript. This library is a solution to such cases when other libraries are not working. And also an alternative for only creating, signing, and broadcasting transactions.
DSteem - https://github.com/jnordberg/dsteem
A Typescript Steem crypto library for node.js and browsers. Steemit Inc also maintains a version of this library
Beem - https://github.com/holgern/beem
A python library to interact with the STEEM blockchain. It includes the CLI tool beempy.
PHP Steem - https://github.com/lukestokes/php-steem-tools
Various tools and scripts written in PHP for exploring the STEEM blockchain.
SteemJ - https://github.com/marvin-we/steem-java-api-wrapper
An API Wrapper for Steem written in Java
GoSteem - https://github.com/go-steem/rpc
Golang RPC client library for Steem
SteemClientRS - https://github.com/cyberpunk-ventures/steem-client-rs
Client library for Steem blockchain built with Rust