The UK Government website is where to find the full list of the trade and mutual agreements signed with non-EU countries.  This includes:

Norway and Iceland  The agreement provides certainty that UK businesses who trade with Iceland and Norway can continue in a no deal scenario, without any additional tariffs.  Read more here

Switzerland - The agreement simplifies trade and allows businesses to continue trading freely, without any additional tariffs. It continues the elimination of duties on the vast majority of goods traded between the UK and Switzerland.   Read more here

 A full list of trade agreements is being regularly updated online and can be viewed at - www.gov.uk