All the ways we have to exchange/trade steem:

PoloniEX (now circle)
Bittrex
Binance
Hobi
Openledger DEX

I see on coinmarketcap a few others I dont know...
HitBTC
Upbit
Blocktrades
GOPAX
RuDEX
BuyUcoin
VebitCoin

Then the decentralized ones that I just don't know. @flipstar, Am I missing any?