Wasabi: Amazon S3-like service, Glacier like pricing. Minimum 1 TB. Minimum lifetime of 90 days.
Backblaze B2. Amazon S3-like service.
Minio: Minimal AWS S3 clone, written in Go.
Storj DCS (née Tardigrade). S3-like service, decentralized.
kahing/goofys: Fast, s3fs-like FUSE layer over S3-compatible object stores.
kahing/catfs: Caching FUSE filesystem. Caches data only, not metadata access.
gaul/s3proxy: Proxy for clients expecting S3 to use a non-S3 store. Java.
Amazon CTO on Past, Present, and Future of S3: high-level description of S3 improvements, including strong consistency
Diving Deep on S3 consistency: more in-depth article S3 strong consistency
Generic (across all services)
rclone: rsync for cloud storage. Used to work with Amazon Cloud Drive, but only works with some fiddling (not guaranteed to stay working). Workaround discussed in https://forum.rclone.org/t/proxy-for-amazon-cloud-drive/2848 (source code at https://github.com/ncw/oauthproxy).
skicka: Google Drive client for Linux provided by Google
Amazon Cloud Drive
See https://developer.amazon.com/public/apis/experience/cloud-drive/content/getting-started for information on getting your client ID and secret.
multidrive: CLI program for uploading to Amazon Cloud Drive
acd_fuse: FUSE adapter for Amazon Cloud Drive
acd_cli: CLI and FUSE adapter for Amazon Cloud Drive
duplicity-acdcli: Plugin for duplicity to upload to Amazon Cloud Drive via acd_cli