World Press Photo, a nonprofit organization dedicated to advancing photojournalism (and hosting a large annual contest for photojournalism) has announced the release of its entire contest archive online. Since the organization has been in existence sine 1955, this is a pretty big archive. There are just under 10,000 photographs by 1,372 photographers of 79 nationalities. The archive is free and available at http://www.archive.worldpressphoto.org/.
There are several ways you can browse this site. You can browse it by year, from 1955 (which has one photo) to 2008 (which has over 60.) Photos for each year are presented in a page of thumbnails, which you can narrow down further by photographer, nationality, organization/publication, category, and prize won. Click on a thumbnail to get a larger version of the photo, and click on the “Photo Information” button to get more details about the people and things in the photo.
You can also browse the archives by photographer (all the photographers are listed in alphabetical order) or you can search. Search allows you to cover a variety of factors including year, photographer, nationality, etc. You can also search by category but this is hit and miss because different categories cover different years. I searched for everything in the “Humor” category (which is actually “Humor and Happy News”) and got 54 results covering 1973 to 1989. Pictures are listed by year, with thumbnails, and it works the same as browsing by year — click on the thumbnail for a larger picture, and on the “Photo Information” button for more details about the photo. Pictures in this category included a baby riding a scuba diver, a very happy winner of a Zulu dance contest, and Ronald Reagan with half a shaved head.