Bitfinex just started supporting a list of new cryptocurrencies:

RLC – iExec RLC

RCN – Ripio Credit Network

REP – Augur

TRX – TRON

ELF – Aelf

AID – AidCoin

SNGLS – SingularDTV

All tradeable for BTC, ETH and USDT.

Bitfinex is one of the most popular cryptocurrency exchanges to date.