https://gitter.im/ethereum

Node Software ("Clients")

Go

https://gitter.im/ethereum/go-ethereum

CPP

https://gitter.im/ethereum/cpp-ethereum

Python

https://gitter.im/ethereum/pyethapp - the client

https://gitter.im/ethereum/pyethereum - the core library (evm, blocks, txs, ...)

https://gitter.im/ethereum/pydevp2p - p2p network

DApp Development

https://gitter.im/ethereum/web3.js

https://gitter.im/ethereum/mist

https://gitter.im/ethereum/solidity

https://gitter.im/ethereum/serpent

Other

https://gitter.im/ethereum/porting

https://gitter.im/ethereum/research

Protocol

https://gitter.im/ethereum/devp2p

https://gitter.im/ethereum/light-client