This site has some basic information on Ireland, this site has information on several other countries and is from the CIA. There is a lot of information and you might want to "skim" it to see what information will be important for you. The reading will not be easy. https://www.cia.gov/library/publications/the-world-factbook/geos/ei.html
This Time For Kids site has information on many countries. http://www.timeforkids.com/TFK/teachers/aw/wr/0,28125,,00.html
This site gives some very basic information about Vikings, you can also explore it to get information about other countries. It is a page for middle school students, so you will have to read it with care. http://www.historyforkids.org/learn/medieval/history/earlymiddle/vikings.htm
Great site with lots of information on many countries Infoplease