I'm going to start a little index of useful solutions for Dynamics 365 - Add a comment with your recommendations and i will check them out and get them added
Do you have multiple files to upload to a record?
Drag and Drop Code from CRMXpress
Autonumbering on more than the standard entities? Complex rules?
eBECS AutoNumber for Dynamics 365
Multiple people working in 1 instance? Track the changes
Change Tracking Solution from Microsoft Labs
Do you have integrations setup Via Scribe
Integration Manager from Scribe
Need to run scheduled workflows? fire in some FetchXML and away you go
Workflow Scheduler from Lucas Alexander