I have used Flickr off and on for the last few months, and finally upgraded to a Pro account because it has become and invaluable way to share and organize my photos.  Recently I received a beta invite to Photophlow and have been trying it out for the last week or so.

The concept is rather simple, but the developers are doing a fantastic job implementing it.  Basically Photophlow is a way for Flickr users to share in real-time their photos with other users.  This is done in a chat environment where you can invite other users or create your own groups.  Users can browse other users photos, search through Flickr galleries,  and display them for everyone else to see.

Users can also rate and comment on the photos shared, and I found it a great way to discover new and interesting photos from Flickr.  Another thing I like about Photophlow is the integration with services such as Twitter and Tumblr.  I use Twiiter regularly and Photophlow can send updates to Twitter about your activity.

Aside from personal use, this could also be a fantastic way to give product demos or tutorials to a group of people.  While I haven't used this for too long, and I'm still learning more about its features, I am quite impressed with the development.  Photophlow is still invite-only, and you can register on their site to receive an invite.  I also have a couple left so if you are interested leave a comment and I will send you one.