Can I create a list based on Opportunities or other objects in Salesforce?

VerticalResponse email lists can only query against fields from Leads, Contacts and Accounts. If you have permissions to utilize the Salesforce Campaigns object, you can run a Salesforce Report on any other Salesforce object, add the Report results to an active Salesforce Campaign, and build your VR mailing list using the "Send emails to members associated with an existing salesforce.com Campaign" option.