Zapier comes to mind for one. What kind of triggers would you want?
- storing incoming invoices in Google Drive
- sending payment reminders (not entirely automated in this case; Zapier just creates a reminder to check and send a reminder by the due date; this could be completely automated, too though)
- storing contracts and project documentation coming in via email
- sending emails to leads at certain stages in the sales process
Zapier’s tools for extracting and programmatically accessing data (e.g. for storing invoices in a folder for the current month) are quite sophisticated.