Web: You'll probably take and check out a lot of photos over the Christmas break. SimpleNeat is the easiest way to create an album, invite others to add their images to it, and share it with anyone.
The webapp doesn't even require you to sign up to use the service. You can just create a new album (which generates its own URL) and share that link with others. You'll have to choose whether to allow others to add photos to the album. Then drag-and-drop images from your hard drive to the window or use the uploader. Give your album a custom name and you're good to go.
You can also sign up at SimpleNeat and save those album links. The free account is ad-supported, and original full-size photos are stored and can be downloaded for a month (and after that, for $0.99 per photo). The Event and Pro accounts increase those limits as needed.
The interface is dead simple for anyone to use and the whole thing looks good too. It's an easy way to get everyone to share their pics and create a collaborative album. You can also do the same thing with Facebook's Shared Album, but well, you'll need everyone to be on Facebook and the interface is not as straightforward.