Very simple password protection to static pages or whole websites with no server configuration required: you ca use Dropbox, Amazon S3 or any generic hosting service to host a private, password protected site.

Password is: password

• Upload the index.html document to the root of your static hosting service.
• Load it up in your browser, enter the password of your choice
• It will show "wrong password", never mind. Copy the section of the URL after the # sign.
• Create a folder with that name next to the index.html file
• Upload the content that you want to protect inside the folder

The final structure will be:

- index.html
- background.jpg
- this-is-a-hash      <-- the SHA1 hash of your password
  \ - index.html      <-- your original index document

• If your hosting service offers directory listing, a visitor can bypass the protection.
• there's no protection against brute force attack. Pick a very long and hard to guess password.
• Pasting the link directly to someone will bypass the login

Credit to @matteobrusa for his initial findings and implementation.