The Bitcoin blockchain can be used for proof of ownership, proof of existence, proof of integrity, etc. It can be used as a decentralized trusted time stamping authority [1]. Try this out for a real implementation: https://proofofexistence.com
It could be used by digital forensics to timestamp digital evidence and prove that it was not "tampered with" during the analysis phase.
The Bitcoin blockchain can be used for many things other than a "currency".