This Australian site Webclass has puzzles and games to practice math facts: http://www.webclass.asn.au/dev/millionaire/siteroot/asp/view/gameIndexBasMaths.asp
The Quia web site provides several games to review math facts: http://www.quia.com/jg/66145.html
Funbrain also has lots of math games. Try out math baseball at: http://www.funbrain.com/math/index.html
The ArithmAttack lets you quiz yourself on your arithmetic facts:http://www.dep.anl.gov/aattack.htm
NRICH is an online maths club for children from 5 to 18, providing free teaching resources for schools and extracurricular activities for maths clubs. It is based in England, and has members from over 80 countries.
The Maya use a base 20 number system. See www.michielb.nl/maya/math.html for more information. Or check on the Egyptian mathematics web site for information on that number system.
Would you like information on the different types of calendars used throughout the world? At the Calendars web site you'll find everything from a description of the Muslim calendar to the origins of Daylight Savings Time.
Want an alternative to the calculator? The Abacus web site will tell you all you want to know about the art of calculating with beads, including a comparison of Chinese and Mesoamerican Abacuses. Oh yes, and it can be viewed in Spanish, German, and French as well as English.