Org Installable Apps

Roll-Up Helper
With Rollup Helper, you can roll-up any Salesforce® data: Count, sum, max, min, average, percent, lookups, text, formula, and multi-currency roll-ups. 
https://appexchange.salesforce.com/appxListingDetail?listingId=a0N30000009i3UpEAI
Mass Action Scheduler 
Create scheduled actions, declaratively and without code.
https://douglascayers-org.github.io/sfdx-mass-action-scheduler/
Declarative Lookup Rollup Summaries (DLRS)
Rollup information between Lookup relationships not previously possible without writing Apex Triggers
https://github.com/afawcett/declarative-lookup-rollup-summaries 
Enhanced Related List
Configure the Filter, Sort, and Fields on this reusable component on any lookup records to group relevant records in a single page (eg: Open and Closed Cases).
https://appexchange.salesforce.com/appxListingDetail?listingId=a0N3A00000FYDY4UAP
OrgData
Copy data from your Production or Full Sandbox environment to Developer/Dev Pro sandboxes. Simply select the data you want to copy, and the app will take care of the rest. No more spreadsheets/scripts/external Ids/ figuring out sequences required.
https://appexchange.salesforce.com/appxListingDetail?listingId=a0N30000009wmCeEAI