iDatabase for Mac - The intuitive personal database manager.
Outlook Google Calendar Sync - Offers calendar synchronisation between Outlook and Google, including attendees and reminders.
Philasmicos Contacts 2 - Philasmicos Contacts is a professional business relationships management system for macOS X.
gSyncit - gSyncit Outlook Cloud Synchronizer. Outlook Calendar, Contact, Task, Note Synchronizer supporting Google, Toodledo, Evernote, Informant, iCloud, AOL, Yahoo, Synology, Fruux, Memotoo and CalDav/CardDav services.
Steward Database - Steward is a personal database for organizing everything. It's easy to use.
EteSync - Secure, end-to-end encrypted and journaled personal information synchronization.