Microsoft's Xim app is surprisingly good, and takes a very different approach to photo sharing.
Most "sharing" app require everyone to have the same app or at lest be signed up for the service. Some just push you pictures out for all to see but Xim is different. It is interactive and engaging in a way I have not seen before.
Instead of everyone craning their neck, squinting at your phone or having to hand over your phone to someone else for them to look at your whole camera roll. You pick the picture or group of pictures you wish to show, select the names from your contacts. Each person receives a text with a link then as a group you can all view the pictures. Each swipe changes the pictures on all of the phones at the same time. If one of the viewers swipes then all do. It is almost magical and quickly becomes a very natural and engaging was you share your photos with the people around you.
It is freely available on the three major platforms, iOS, Android and Windows
www.youtube.com/watch?v=huOqqgHgXwQ
http://www.getxim.com/