Britannica Online - Elementary Edition
Search for your country or use the World Atlas link in the Features section.
Yahoo! Kids World Factbook
Check here maps, flags, and fast facts. It also has lots of information on your country's economy, government, and resources in particular.
National Geographic Kids
Find your country on the list, then use the arrows to page through the different facts about the country. Also check out the map tab.
If you can't find information for a specific section, move on to the next. Once I see where groups are having trouble, I will add more targeted sites to use for those questions. Happy researching!
You asked for it, so here it is: information on the Mexican flag.