1. ETL: Fivetran / Stitch Data / Airbyte. Industry standard has become Fivetran at this point. Airbyte is open-source and cheaper so it's becoming more commonly used too - https://fivetran.com/ - https://airbyte.com/

2. Reverse ETL: Census / Hightouch / Airbyte. Hightouch seems to be the most popular and well-liked for Reverse ETL. Airbyte acquired grouparoo so they have reverse ETL too. - https://hightouch.com/ - https://airbyte.com/

3. 2-way ETL: Bracket / Retool Bracket syncs data directly into SaaS tools via SQL logic and can sync back changes from SaaS tools across those joins. Retool can do the same but onto Retool dashboards / internal tools instead of using existing SaaS tools. - https://usebracket.com/ - https://retool.com/

Old Age Mulesoft, Matillion, Piesync, etc. Some are acquired, some are just used by older companies and are more bloated. I don't know any newer companies that use these tools.

re-commenting the links below