In a similar way to the idea behind Unhosted, you bring your own data (i.e. photos) and the application does something with it (i.e. display them nicely, allow you to share them easily). I’m using Dropbox, but you can use Amazon S3, Box.net and more.
I like openphoto.me. I’ve uploaded two sets, one public and one private. The private one is of my children and shared only with family. The public one is of some photos I took down at Druridge Bay yesterday.
Where do you store your photos? Why?