Scaling is one of the biggest challenges Ethereum is facing today. There are a lot of proposals and approaches to the problem. Here is a list of the most know scaling solution proposals:
- TrueBit
- Raiden Network aka. State Channels
- 0x Protocol
- Plasma
- Sharding
- Casper - Proof of Stake
- Cosmos
- Polkadot
For more detailed info please visit BlockchainHub - Scaling Ethereum