SpiderOak - SpiderOak makes it possible for you to privately store, sync, share & access your data from everywhere.
Cyberduck - A libre FTP, SFTP, WebDAV, S3, Backblaze B2, Azure & OpenStack Swift browser.
Duplicati - Free backup software to store backups online with strong encryption. Works with FTP, SSH, WebDAV, OneDrive, Amazon S3, Google Drive and many others.
Bucket Explorer - Amazon S3 gui client Bucket Explorer to create and manage bucket, for web hosting and sharing S3...
CrashPlan - CrashPlan for Small Business backup software offers the best way to back up and store business & enterprise data securely - offsite, onsite & online in the Cloud.
S3 Browser - S3 Browser is the name of an easy and simple to use Amazon S3 clients for the Windows operating systems.