The Google/LIFE archive was announced in 2008 and after doing some…well…Googling, I found that it was moved around a bit and even taken down. Its back now and has more photos than ever. You can go to the official Google LIFE Search site or just do a Google image search and add “source:life” For example Apollo source:life
The best news is that many of these images are in the public domain, so they can be used without any concerns of plagiarism! Look to the bottom of the image to see what rights are ascribed to it.