According to Wired News,

Gadget nerds: Prepare to lose the rest of your day to awesomeness. PopSci, the web-wing of Popular Science magazine, has scanned its entire 137-year archive and put it online for you to read, absolutely free. The archive, made available in partnership with Google Books, even has the original period advertisements.

This is awesome! I can check the advertisements for 100 years ago in the archives. The cover images are priceless.