WebDrive maps a network drive letter to your remote servers and cloud storage, allowing you to access files in a way that’s consistent with the way you already work. WebDrive provides file access through the familiar interface of Windows Explorer or Mac Finder — and from within every desktop application. This instantly familiar interface reduces training and technical support effort.
I started using Webdrive about 5-6 years ago when my company implemented it to connect to our Sharepoint server. I've used it for SFTP, and to automatically backup my files to S3. It just makes getting to your files any where in the cloud the same as getting to them on your PC. I use it all the time, but rarely think about it. Kind of a set it and forget type of thing. I've used their tech support a couple of times over the years and have found them to be helpful.
odrive - odrive aggregates all cloud storage. Access, sync, share, and encrypt everything in one place. Integrations to 20+ storage services, desktop sync, Linux support, placeholder files, zero-knowledge-encryption, web client, advanced sharing, and more!
ExpanDrive - ExpanDrive is a fast network drive and browser for cloud storage.
Koofr - Koofr offers safe EU based cloud storage with free storage space for life and options to connect multiple cloud accounts (Dropbox, Google Drive, OneDrive) and your personal storages.
NetDrive - Cloud storage as hard disk
CloudHQ - Integrate Box, Gmail, Salesforce, Google Drive, Dropbox, Basecamp, Evernote, and more.
Cyberduck - A libre FTP, SFTP, WebDAV, S3, Backblaze B2, Azure & OpenStack Swift browser.