LensFolder.com is free of charge, with the company noting on its FAQ page that it may use an ad-supported business model in the future. The idea behind how the site works is rather simple and elegant. The first person to visit the site after the event creates an online "folder" that will be used for all photos from the event, and distributes the username and password for the folder to the other attendees. A valid email address is required to do so, as a confirmation link will be sent to the registered email address. Everybody then uses the login details to upload their photos to the folder. The same username and password is used to log in and download all photos from the folder, allowing attendees to download the entire set of photos in one go. After one month of inactivity, LensFolder automatically purges the photos from its system.
Currently, LensFolder only supports JPEG still images. Raw and other still image formats, as well as videos, are not supported by the site. It does also require some communication between photographers outside of the site, since there's only one group login credential for the folder, and no way for the site to contact individual attendees to let them know as new photos are added. Aside from those limitations, though, LensFolder looks like a very useful solution for sharing public event photos.