WorldUFOPhotos offers a wonderful collection of strange photos, some most likely authentic, but we're not doing any evaluations. To my eye, the strangest one is the floating object on Mars. NASA hasn't commented, of course.
Nuthin' I love more than a collection of pre-Photoshop UFO pictures that the debunker trolls can't immediately cry "fake" on. Before I clicked on the link I had a particular old picture of a UFO that I remember from my childhood come to mind, and it was on the first page that came up. :D (Image #14, page 1, 1965 Tulsa, Oklahoma--Alan Smiths Photograph)