Doesn't appear to be much info on bitcoin cash on steemit, but it seems to be a popular topic.
Officially it happened on block 478558.
Here are some relevant links:
https://www.btcforkmonitor.info/
https://coinmarketcap.com/currencies/bitcoin-cash/#markets
Exchanges currently trading BCC/BCH:
https://yobit.net/en/trade/BCC/BTC
https://hitbtc.com/exchange/BCCF-to-BTC
https://www.viabtc.com/quot/realtime?currency=btc&dest=bcc