I heard bitfinex will also credit bitcoin gold to it's users.
Hitbtc will be credited and trading also will be allowed for it's users.
For bittrex it will only credit it's users and it will not enable trading for it's user's.
Coinbase as far now, is not supporting bitcoin gold, the bitcoin gold dev team have left a message for them on their site, so coinbase might change it's plans, otherwise no.