http://whenshouldivisit.iamdanw.com/ via @annadph
born out of the fiery genius of Culture Hack Day 2011
[UPDATE: Absolutely didn't mean to write more about this - but following Dan's insistence that it is a joke and that everything doesn't need to be turned into software and people should just ask the museum, I went in search of daily visitor patterns within each of the museums involved... Tate positively encourages people to come on a Saturday - instead of saying you'll have a better time if you come on Weds.
Likewise none of the other institutions offer this kind of insight. So, actually, this is, probably the most effective way to know that. And that is useful. Newspapers print it. people appreciate it. even if it's obvious. especially when, as a joke, it's not exactly that funny]