Uniswap is a decentralized exchange that facilitates automated transactions between Ethereum-based tokens. It is designed to be an open-source platform with an automated market maker (AMM) model. Instead of using an order book, token trades are facilitated directly between users through a liquidity pool and prices orders with an algorithm that relies on the equation x*y=k to create a price spectrum for token pairs available in the liquidity pools provided by other users. Uniswap tokens are used as a governance token and as an incentive for users to fund the liquidity pools. Since the platform is decentralized, all the trading fees collected are distributed among the liquidity providers; according to the share that they provide in the liquidity pools.
Uniswap is one of the largest decentralized exchanges (DEX) and one the largest cryptocurrency exchanges overall by daily trading volume. The platform was originally created by Hayden Adams, a former mechanical engineer at Siemens. It is backed by some influential venture capital funds, including: Andreessen Horowitz, Paradigm Venture Capital, and Union Square Ventures.

0x is a decentralized exchange built on the Ethereum blockchain that allows for ERC20 tokens to be traded. 0x hopes to serve as a building block for creating decentralized exchanges.
It is an open-source system of smart contracts that acts as a platform for those wanting to build with the 0x protocol. Augur, Aragon and several other projects are using 0x, at the moment.
The 0x protocol addresses some of the common issues that plague other decentralized exchanges. 0x is faster, more liquid, and less expensive to run. Its speed is due to reduced blockchain congestion. This is achieved by moving all transactions off of the blockchain and then verifying them. This move, also allows for the elimination of transaction fees by reducing the reliance on the blockchain. 0x doesn’t charge fees of any type to use the protocol. However, Relayers that create their own decentralized exchange can charge fees.
The 0x Project uses the 0x Ethereum token, known as ZRX, that allows users to pay Relayers’ transaction fees. It is also a decentralized form of governance for the 0x protocol system. Anyone holding ZRX can give input about improving the protocol.

The Balancer cryptocurrency is the reward token that fuels the Balancer market maker protocol. The Balancer protocol serves as a liquidity provider and a non-custodial portfolio manager. Unlike other automatic market maker protocols, such as Uniswap, Balancer is designed to provide a general solution that can be customized for a variety of trading pools with different distributions. It uses smart order routing to send trades to trading pools with the best rates available, and rewards traders by paying them a fee for increasing the liquidity of these pools.