Newspapers are fun resources but they can be difficult to find. Here's some of my favorite free online newspaper sites to help you get you started:
Elephind searches several of the largest digitized newspaper collections simultaneously. Type keywords and phrases into the search bar and get results from newspaper archives from across the world.
Google News Newspaper Archive
Google created a great collection of digitized newspapers. Unfortunately, the collection is not keyword searchable. Find the name of the newspaper you're looking for and browse the paper like digitized microfilm.
The Ancestor Hunt: Newspaper Links
This blog hosts an exhaustive list of online newspaper resources for each state. If the newspaper you're looking for isn't listed here, it's probably not online yet.