An open-source distributed storage service you can self-host to fullfill many needs. Can do everything from hosting to working as a backup target. Designed to make it easy to have multiple replicas in widely geographically dispersed locations.
Comes as a single no-dependency executable. Written by sysadmins, so they understand how much you don't want to dick around with stuff until it works. Tries to be as resilient as possible. If you really want, you can run a copy on everything you own to build a storage field. Has very lightweight hardware requirements. Implements the S3 API.