DropEvent - Collaborative Photo Albums via Email

Drop Event is a free service for creating public and private group photo albums. To create a group photo album you do need to register for the service, but contributors to your photo album don't need to register. When you create your photo album it is assigned an email address that contributors can send photos to through email. To invite people to contribute to your album, just give them the email address assigned to your album.

Thanks to Kristen Swanson for the info about Drop Event.

Applications for Education
If you've ever wanted to have your students contribute to a group album, but were deterred by the requirements for students to create accounts, Drop Event could be the solution you're looking for. Using Drop Event photography students could email contributions of their works to an album. Recently take students on a field trip? Have them and their parents email contributions to a group album.