I can't speak for the capabilities of Salesforce, but the Act application itself doesn't have any support/integration for use with Salesforce. Though obviously both programs can import/export spreadsheets etc.
However - you can connect Act! to Zapier through Act! Connect. I know Salesforce is also able to connect with Zapier - so there is a path that data could be shared between the two. It would depend on the requirements of the integration as to how well this would work.
Could you go into a little more detail about what would need to be shared?