An Ethereum mixer based on ring signatures and stealth addresses

Kendrick Tan picked up on Vitalik's recent request for product (a Uniswap-like interface for mixing ETH) and hacked together heiswap. It's now live on Ropsten.

This is obviously much needed and super cool and great to seem more teams addressing this need, however there are a number of limitations to the current implementation, as pointed out by Kendrick and other observers. Namely it can only de-link the sender and recipient addresses (not amounts), it requires participants to send ETH in fixed denominations and is not instant (as it needs more deposits to be able to mix properly). Another critique raised by Udi is that in order to withdraw the mixed ETH one needs some (unmixed) ETH to pay for tx fees, so if one is mixing own coins rather than sending them to a third party it risks de-anonimyzing the tx.

It will be great to see more work on it, particularly on the incentivization layer which would fix some of the issues highlighted about.

heiswap.exchange
Github repo

"Kiva for DAI"

This is another beautiful example of protocol modularity allowing for new use cases in Defi. In this case, it's about solving the structural inefficiencies of traditional credit systems, particularly for borrowers in developing nations that struggle to leverage their credit rating in order to access loans at sensible terms.

The team behind this are the winners from the recent Gitcoin + MSFT virtual hackathon at the Ethereal Summit, and what they are building as an open-source project allows lenders to make stablecoin microloans to emerging market borrowers in a borderless, P2P fashion.

They are using a combination of DeFi protocols, such as Bloom for identity attestation, OpenZeppelin's ERC20 for the crowdsale contract and Dharma's Loan Contracts for debt token issuance. They just got a 3-month grant from Binance to fund a security audit.

Enable Github repo
Co-founder tweetstorm

A simple interface to refinance your MakerDAO loan on Compound, or vice versa.

The Instadapp team continues to make Defi more usable and accessible with a neat way of moving your Maker CDP to Compound in one transaction (instead of 12!), allowing borrowers to swiftly flow between lending protocols depending on market rates (right now saving on fees and earning on the collateralized ETH). Market forces inevitably at work in a permissionless world, making defi more efficient to the benefit of ens users. It will be interesting to watch the impact on Maker stability fees/DAI peg.

Medium post
instadapp.io/bridge

Instant token swap at the best price across all DEXs.

As anticipated back in May, the Totle team have released a dead simple interface for exchanging ERC-20 tokens that automatically goes off and fetches the best price available from decentralized exchanges they integrate with, hiding all those complexities in the background. 
The very cool thing here is that the user submits one single transaction and the Totle smart contract executes multiple buys and sells over multiple DEXs.

swap.totle.com

Ethereum token swap aggregator with best possible price achieved by splitting volume among DEXes inside single transaction.

This is a project born over a weekend at the latest ETHNewYork hackathon and, along the same lines as Totle Swap, it automatically splits up a token swap transaction across multiple orders over several integrated DEXes (eg UniswapExchange, KyberNetwork, Bancor and RadarRelay) in order to minimize price slippage. By using the Gas Token they are also able to bring down tx costs. 

The creator of the Uniswap ROI calculator has recently created a similar tool for Compound. Type in your Ethereum address and the net position is worked out, with a more detailed breakdown on how your investments or borrowings are driven by price movements and accrued interest.