Ethereum

Ethereum has and always will be one of the biggest alt-coins of all times. Not only is it fast and has low transaction fees, but it also acts as a platform for other projects to build upon by using their smart contract technology. Ethereum has a ton of developers backing it and making contributions to the codebase, many roadmap plans to handle future needs and a big community. The biggest Ethereum feature is smart contracts, which is basically code that automates transfers on the block-chain based on certain trigger conditions being met. Many applications are being built based on the smart contract technology and I don't see that going away any time soon.

EOS

EOS is a platform for developers to easily create decentralized applications, which are applications that rely on smart contracts to interact with the block-chain. Smart contracts are simply contracts or code that executes when certain conditions are met, for example you might use a smart contract to automatically send 10 ETH to your friend once their favorite football team wins a match. EOS will essentially accelerate the types of applications that can be built on top of the block-chain and pave the way to the next wave of decentralized applications. Some people say it will be an Ethereum killer, but will will have to see about that.

Salt

SALT is essentially a lending platform for crypto-currencies, no this is NOT a bitconnect copy-cat. With the salt lending platform you can lend your crypto out to them in return for cash you can spend in the here and now. What is the advantage of this versus simply selling your crypto and sending it to your bank account? YOU DON'T PAY TAXES ON LOANS. This could potentially be HUGE if the tax-exempt status is confirmed. Right now there are many people making money in the crypto space, but most of that money falls under short term capital gains which means it is essentially added to your income when you pay taxes. If you make 50k/year and made 20k in crypto, your effective salary is 70k for tax purposes.

Powerledger

Power ledger is going to revolutionize the solar and energy marketplace, it will allow people with excess energy produced by solar panels or other renewable sources to be bought and sold on the block-chain. Instead of simply passively getting energy from your local power station and letting them decide what to do with your excess electricity, you will be able to decide what to do with the excess energy you produce and profit off of it. Power ledger is also backed by the Australian government, who gave it an 8 million dollar grant to work on it's technology and infrastructure.