The "European Heritage Days" (French: "Journées européennes du Patrimoine") are held in several European countries, most prominently France, on certain days in September. On these days, many buildings not usually open to the public (e.g. the Élysée Palace) are open for visiting, as are the workshop of certain artisans (e.g. stained glass window specialists, or sculpture restorators).
I suggested and implemented on the French Wikipedia the following scheme: a sitenotice mentioning the event and pointing out that the general public can help Wikipedia get more photos, with a link to a page explaining how to contribute photos. This page gets 7000-8000 hits daily.
We eschewed telling people about the upload interface - instead we explained to them in layman's terms what a "free license" is and told them to send pictures by email to the permissions-commons-fr OTRS address.
This action was mentioned on several online news sites, including Ecrans.fr (the Internet-related news site associated with the daily Libération).
We used this occasion to point out to users some of the difficulties we have with public museums and monuments in France. On Wednesday, I published an op-ed in the national daily Libération explaining how our current policies are ill-suited. There are chances there could be changes, according to a recent report I received from the Minister of Culture, which seems to endorse certain suggestions I made to the Ministry when I was heard in 2008 before a commission there, on behalf of Wikimedia France.