I had mentioned in the previous post, that I do participate in a photo sharing community that is called "Capture Wisconsin" and "Capture Minnesota." I believe there are numerous iterations of this "Capture", even down to cites ("Capture Chicago"). Like most other social media sharing sites, you post pictures, add titles, captions and tagged with categories. People can "dig it", "love it" , follow photographers and add comments that you can reply to. The sites have moderators/editors, who select Pictures Of the Day and post daily picks as well. The site controls for location (you have to include where the photo was taken and if it is outside the defined boundaries, it doesn't get in), there is a request to not upload photos that are heavily photo-shopped or include extras, such as text, stamps, etc.
I know of Instagram, but hadn't been interested enough to check it out. Our institution does have an Instagram account (just now discovered), where events -- such as National Library Week -- are captured and shared. In my particular library, I don't think we have utilized this account -- something to bring up at our next communications meeting.