There are literally hundreds, if not thousands, of recreational math websites, especially those devoted to solving easy, medium, and hard puzzles. The following is just a taste of what is out there:

BrainBashers

http://www.brainbashers.com/puzzles.asp

A great site with many listings of puzzles—for younger and older puzzle aficionados.

Easy Calculation

http://www.easycalculation.com/puzzles/easy/easy1.php

This site offers what it advertizes, including puzzles that are simple to a definite challenge for some. It also offers other information about solving mathematical calculations, including many calculators (for example, a mortgage calculator) and conversion sites.

Interactive Mathematics Miscellany and Puzzles

http://www.cut-the-knot.org/content.shtml

A little bit of everything, from games and puzzles, to fallacies and visual illusions.

Mathpuzzle.com

http://www.mathpuzzle.com

Another great site for recreational math and puzzles.

Puzzles.com

http://www.puzzles.com

Illusions, puzzles, tricks, and toys can be found here. There is also a gift shop, puzzle links, and help.