The Digital Public Library of America or DPLA intends (see their goals here) to build one single location (or “portal”) from which anyone may search all Open Access public library resources online (using data shared freely with them by institutions in the USA). This approach has good support from the US library community (see this ACRLog entry).
One innovation is that the DPLA publishes information (application programming interface or API) that independent developers can use to create their own software tools (applications or apps). As the DPLA site says, “Developers make apps that use the library’s data in many different ways.”
I visited the DPLA App Library and played around with OpenPics the other day. I appreciate that it is offered without cost to users and is intended to inspire open and cooperative improvement. But as it stands now, I found the software lacking in sufficient resolution or metadata/source information to even consider at this time as useable for scholarly purposes. I would recommend that anyone interested keep an eye on this site, though, as these apps are likely to improve along with the impressively growing scale of the DPLA library itself.