UPDATE: The Swap Challenge has ended - However, you can try out mainnet Bitcoin, Ether, DAI, USDC, USDT, and WBTC Atomic Swaps at Liquality!
Edit: Check out Atomic Swaps in action via Liquality's products:
* Atomic Swap Wallet - Tutorial
* Atomic Swap Interface - Tutorial
TLDR; swap your Rinkeby testnet ether