List of Bitcoin exchanges and wallets with information about supporting Bitcoin Gold
Bittrex supprting, but deposits closed already. Their post here.
HitBTC supporting both Bitcoin Gold and Segwit2x. Their post here.
Bitstar has announced their support for BTG on their announcement post here.
Coinbase info from their blog post
Poloniex might distribute BTG depending on the replay protection fix, they posted today about it here.
Gemini no statement about it yet
Mercatox no statement yet
Wex no statement about BTG yet
Ledger Nano S no statement about it yet, but there are reports that as long as your BTC are stored in “legacy” or “segwit” wallets then once replay protection is setup for BTG then you’ll be able to redeem your BTG tokens.
Mtgox is not supporting Bitcoin Gold