Say you want to share your photos with family and friends but you don't have a website, don't want to email the pics, and you don't want to sign up for a flickr account.
Here's something else: picupine, a simple pic sharing with no sign up. You can upload your photo and get a URL you can email - the link will stay active for a week, then it will automatically expire.
Link - Thanks Luke! (I wonder what they get out of it?)