LIFE Magazine's Pictures Online

From the website:

Welcome to LIFE.com, the largest, most amazing collection of professional photography on the Web.

LIFE and Getty Images, the two most recognized names in photography, have joined forces to provide you instant access to millions of breathtaking photographs — for free. LIFE.com not only lets you wander through the legendary LIFE and Getty archives, but with more than 3,000 new photos added every day, it also gives you the best pictures of the people and places shaping our world now.

Thanks, Danielle, for the tip!