Keybase.io is a new project and open to everyone to join. The project is still in alpha. Sometimes signup is by invitation only, other times signup is wide open. Even though the project is in alpha the crypto is based on standard PGP.
Public Key Storage Directory
Keybase holds, displays and verifies your public key. Connect twitter or facebook accounts to verify you are who you say you are. Like any service, you can add only what you want to add. The theory is it may be easy to hack one website and change the key or the fingerprint of the public key. It's much harder to hack facebook, twitter, github and the other sites they support and list your public key. You can verify the fingerprint of a public key on multiple locations and with some certainity, be sure you have the right public key and it's not being spoofed.
Keybase also has encrypted disk storage not hosted in the cloud, it's peer to peer. Keybase creates an encrypted directory on your drive. There are public and private directories and you're able to create a private directory with chosen people. File directories are limted to 10gb.
Clients and Command Line
Windows, Linux and Mac desktop clients are supported. There are some command line only options, but the documentation is pretty good. This may be advanced for a few, but if you understand PGP concepts (private / public keys), this should be easy to follow.
10gb file limit
For transfering larger files, 10gb or less, this may be one of the best and secure options. Create and share a private directory, place your file(s) in the directory and a notice is sent to the person that a file is being shared.
Accessible Over Onion
Keybase.io also has a secure chat client and is accessible over TOR at fncuwbiisyh6ak3i.onion