During a year, David Peterman documented every one of the 347 free-standing USPS mailboxes in Seattle, and posted a series of photographs on the blog Mailboxes of Seattle.
On the blog, he explains why:
Why am I doing this? That’s a damn good question. (...) Finally, yes, I’m fully aware that this is an absolutely meaningless pursuit. Hurrah for the internet.
(From David Peterman's blog Mailboxes of Seattle)
You can listen to an interview with David Peterman on the Postcardist Podcast, if you want to know more about this project. Or just go to see the over 350 pictures of mailboxes, and the stories that come with them.
The whole project fascinates me. Among others, the fact that he only saw like four people actually dropping mail during the whole year.