I know this thread is a tad old and I'm sorry for bringing it back up, but for anyone wondering:
Alterantiveto.net
This site allows you to search through anything. For instance, if you type in Flickr and click search, it'll list all the alternatives out there. Free, Commerical, and Freemium. It's not specific to photography. It'll show alternatives to just about anything. Great resource if you need to find something (it does list alternatives to android apps, iphone apps, etc. Not just for windows or mac).