Almost every public library has a strong online presence, and city library sites are normally spectacular. Boston Public Library has some collections on flickr, including 351 travel posters from the 1920s and 1940s, when the average person could seriously travel if he wanted because of railways, luxurious ocean liners, and good highways. "Travel agents and ticket offices during this period were festooned with vivid, eye-catching posters, all designed to capture the beauty, excitement and adventure of travel." Now these same posters make nostalgic and artistic statements about a time long gone.
The CIA World Factbook is a fantastic online resourse that includes maps, flags, and detailed information about every country in the world. The blog post from Government Book Talk discusses CIA history, and how the Factbook is compiled along with the purpose it serves.
Students and teachers can now access and manipulate local Census data, based on samples from 2005 to 2009. (The Times notes that the data is based on samples and subject to a margin of error, particularly in places with lower populations.)
Maps are available for race and ethnicity, income, housing and families, and education. Within each category, researchers may filter by a variety of related subcategories. Data are searchable by address, zip code and city. Maps are scalable and a simple shift of the mouse allows you to examine patterns and differences among and within communities.