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