Photos: Need to find dupes & sharing

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I've got quite a lot of duplicates in my iPhoto library and was wondering if there was a quick and easy way of identifying these and deleting them, maybe some software which will do it for me?

Also, I would like to create some online library for my photos so that others can look at them as well (private access though not public) what is the best app/website to do this? Photostream? Flickr? Dropbox?

Thanks for any suggestions.