MathPuzzle.com is an unusual...but interesting web site. It takes effort to browse it, but it has some interesting information on it...i.e the browse reaps benefits.
In the manner of Martin Gardner, this web site celebrates math puzzles and Mathematical Recreations. It is maintained (but not very regularly) by Ed Pegg Jr. of Champaign, IL. Consider his Wiki-bio: "Expert on mathematical puzzles and is a self-described recreational mathematician. He creates puzzles for the Mathematical Association of America online at Ed Pegg, Jr.'s Math Games. His puzzles have also been used by Will Shortz on the puzzle segment of NPR's Weekend Edition Sunday. In 2000, he left NORAD to join Wolfram Research, where he collaborated on A New Kind of Science. In 2004 he started assisting Eric W. Weisstein at Wolfram MathWorld. He has made contributions to several hundred MathWorld articles. He is one of the chief consultants for Numb3rs. Impressive...!
In addition to the opening discussion linked above, the website offers discussions about puzzles in these categories:
I found it interesting to just browse through the many pages and think about some of the suggested problems. The variety of content offers avenues for further work or explorations on your part.
One of the "unexpected" pages was that of Prize or Contest Problems. That is, it is a listing of problems where someone is offering money for its solution. A good summer job?
If not, the page of links, plus the many links at the bottom of the home page, should keep you busy during the summer as well....A Puzzle Thought a Day Keeps...