This is my information dump of o365 add-ons and tools. I’m just starting it so I’m sure I’m missing some.
SkyKick – o365 migrations including public folders, only sell through resellers ( Can also do backups. But only sells to microsoft partners)
BitTitan – o365 migrations including public folders, direct sell, primary product is migrationwiz
Sharegate – sharepoint migrations to from onprem to o365 only
MessageOps – Lots of different tools but the Office 365 Exchange Migration Tool allows you to import AND export pst files. This is the only tool I’ve found that allows you to do this.
0365 Manager Plus – ManageEngines option for delegated o365 admin
Office Quick Starts – Get up and running quickly with our new online Office Quick Starts.
Spanning – An Kaseya company, hard to find details just talks about backing up o365.
CloudAlly – Can backup both Sharepoint and online Exchange. Looks like Sharepoint and Exchange are different solutions so you are charged differently for each.