We just launched a Private Set feature for all pro account holders.
This feature allows you to assign passwords to sets of images in your portfolio. You can use one password for multiple sets, or different passwords for different sets. Once you assign a password to a set, it will become invisible to visitors and an “Unlock Sets” link will appear on your portfolio allowing users to access them.
This feature gives you a chance to lay things out before the world sees your new work, and is especially useful to share works in progress with clients.