Atomic swaps promise to cut out the middlemen and a few blockchains promise to support it.

Atomic Swaps Between Litecoin and Vertcoin are in the Works

http://www.newsbtc.com/2017/09/21/atomic-swaps-litecoin-vertcoin-works/

Decred Adds Atomic Swap Support for Exchange-Free Cryptocurrency Trading

https://bitcoinmagazine.com/articles/decred-adds-atomic-swap-support-exchange-free-cryptocurrency-trading/