Where can we collect and share photos online without having to sign up?

Gabriel's organisation works with community groups on volunteering, and they want to collect photos of all the various projects as simply as possible

Once a year we hold a big day of international volunteering. Community groups, churches, synagogues and so on organise their own projects under our banner. We encourage them to take photos of their project and send them to us.

We would like to find a system that lets them upload photos easily, to a secure folder, without having to sign up for accounts or anything. We would then download the photos centrally, categorised by who uploaded them. DropEvent is the sort of thing we want, but it just gives us a big glut of photos without them being categorised into folders based on who uploaded them.

DropEvent's big idea is "everyone's photos from your wedding in one place," though it could equally be your Christmas party, school play, or whatever. Another attraction is that people can upload photos without having to sign up, though they still have to enter their email address.