I recently created an account at Stumble Upon and often while I feed Baby K I peruse the websites that are matched to my selected interests. Off the top of my head, some of the subjects are history, geography, science, education, music, books, etc.
Shocking, I know.
Here are some pages that I have thought were worth bookmarking.
The Size of Our World
Spectacular Trees From Around the World
World Sunlight Map
Arrow of Time
Young Me/Now Me
Test Your Geography Knowledge