Here is a site that updates puzzles regulalry:
 mathschallenge.net
  • Irrationality Of E 17/10/2010 01:00

    Prove that e is irrational.

    Problem ID: 377 (17 Oct 2010) / Difficulty: 4 star
  • Rectangle Construction 17/10/2010 01:00

    Find the connection between the constructed length and the original rectangle.

    Problem ID: 376 (17 Oct 2010) / Difficulty: 2 star
  • Inscribed Circle In Isosceles Triangle 16/08/2010 01:00

    Find the radius of the circle inscribed inside the isosceles triangle.

    Problem ID: 375 (16 Aug 2010) / Difficulty: 2 star
  • Multiplying Magic Square 16/08/2010 01:00

    Show how the values 1, 2, 4, 8, 16, 32, 64, 128, and 256 can be placed in a 3x3 square grid so that the product of each row, column, and diagonal gives the same value.

    Problem ID: 374 (16 Aug 2010) / Difficulty: 3 star
  • Polynomial Roots 07/08/2010 01:00

    Prove that the roots of the polynomial, xn + cn-1xn-1 + ... + c2x2 + c1x + c0 = 0, are irrational or integer.

    Problem ID: 373 (07 Aug 2010) / Difficulty: 3 star
  • Hops And Slides But Never Square 07/08/2010 01:00

    Prove that the minimum number of moves to completely reverse the positions of the coloured counters can never be square.

    Problem ID: 372 (07 Aug 2010) / Difficulty: 3 star
  • Irrationality Of Pi 24/12/2009

    Prove that π is irrational.

    Problem ID: 371 (24 Dec 2009) / Difficulty: 4 star
  • Square And Round Plugs 24/12/2009

    Which fits better... a round plug in a square hole or a square plug in a round hole?

    Problem ID: 370 (24 Dec 2009) / Difficulty: 2 star
  • Algebraic Cosine 30/11/2009

    Prove that cos(x) is algebraic if x is a rational multiple of Pi.

    Problem ID: 369 (30 Nov 2009) / Difficulty: 4 star
  • Inscribed Square 30/11/2009

    Find the side length of the square inscribed inside the right angled triangle.

    Problem ID: 368 (30 Nov 2009) / Difficulty: 2 star
  • Infinite Circles 15/11/2009

    What fraction of the large red circle do the infinite set of smaller circles represent?

    Problem ID: 367 (15 Nov 2009) / Difficulty: 4 star
 Scientific American - Math
  • Readers Respond to "A Crisis In Physics?" 23/08/2014 16:15
    Letters to the editor from the May 2014 issue of Scientific American

    -- Read more on ScientificAmerican.com
  • What Is the Goal of a Math History Class? 22/08/2014 13:30
    I'll be teaching a math history class for the first time this semester. I'm excited to be teaching it, but I've noticed that preparing for this class has been very different from preparing for other...

    -- Read more on ScientificAmerican.com
  • Science Media Beset with Gender Gaps 21/08/2014 20:52
    In the fall of 2005, I and a couple hundred other new students at Columbia University's journalism school walked into a lecture hall for a series of welcome speeches, and two things happened that...

    -- Read more on ScientificAmerican.com
  • Physics Week in Review: August 16, 2014 16/08/2014 10:21
    This week on Virtually Speaking Science, I chatted with astrophysicist Katie Freese, author of a new book, The Cosmic Cocktail: Three Parts Dark Matter.

    -- Read more on ScientificAmerican.com
  • Iranian Woman Nabs Highest Prize in Mathematics 13/08/2014 19:00
    Maryam Mirzakhani is among four young researchers to win the 2014 Fields medals, which are awarded every four years

    -- Read more on ScientificAmerican.com
  • Diversity in Focus at Upcoming Science Writers Meeting 12/08/2014 22:49
    Calling all journalists, authors, editors, producers, public information officers, students and communicators with a passion for science, tech, engineering and mathematics!

    -- Read more on ScientificAmerican.com
  • How to Talk About the Fields Medal at Your Next Cocktail Party 11/08/2014 18:08
    On Wednesday, four mathematicians will receive the prestigious Fields Medal at the International Congress of Mathematicians (ICM) in Seoul.

    -- Read more on ScientificAmerican.com
  • The Glory of Math Is to Matter 11/08/2014 13:00
    In 1842, when the famed German mathematician Carl Gustav Jacobi was invited to speak to a scientific meeting in Manchester, he had a surprise in store for his English hosts.

    -- Read more on ScientificAmerican.com
  • Skulls, Bloodletting, and How to Teach Science 07/08/2014 17:44
    [View the story "Skulls, Elephants and How To Teach Science" on Storify]

    -- Read more on ScientificAmerican.com
  • What will the future of education look like? 06/08/2014 12:00
    Scientific American's August supplement takes a look at the changing landscape of education in the face of emerging technology, and asks the question, how do we increase interest and engagement in...

    -- Read more on ScientificAmerican.com
  • What predicts NBA success? 06/08/2014 02:28
    “To an outsider watching Pop Herring’s basketball tryout in November 1978, it would not have been obvious that the gym at Laney High in Wilmington, N.C., held a player destined to become...

    -- Read more on ScientificAmerican.com
  • Physics Week in Review: August 2, 2014 02/08/2014 10:36
    Looking for a few good popular math books? In the latest New York Times Book Review, I look at five terrific recent ones: Jordan Ellenberg's How Not to Be Wrong, David J.

    -- Read more on ScientificAmerican.com
  • Comedians Do Everybody Good (Researchers Included) 31/07/2014 20:03
    In my perfect world, artist-in-residence is just the beginning. In my perfect world, all researchers and research institutions are paired with a comedian-in-residence.

    -- Read more on ScientificAmerican.com
  • Math Twitter Bots, Reviewed and Rated 28/07/2014 13:00
    In the course of being a math person on Twitter, I have run across some math-related Twitter bots and feeds. It would just be mean to grade my human tweeps, but I have no qualms about rating the bots!

    -- Read more on ScientificAmerican.com
  • Mysterious Tiles from a Time When Art and Science Were Friends 25/07/2014 17:44
    Forces in society of late have lots of us longing for the days of the Enlightenment, smallpox, powdered wigs, ridiculously uncomfortable clothing and all.

    -- Read more on ScientificAmerican.com
  • The Shocking Failure of British Rail Travel to Respect the Triangle Inequality 23/07/2014 13:00
    I spent about a month in the UK earlier this summer, and that meant I took a lot of train trips. I love riding trains: the feeling of endless possibility I get when I look at the departure boards,...

    -- Read more on ScientificAmerican.com
  • When was the last time you used a print dictionary? 22/07/2014 13:39
    I used to keep a small dictionary in my bedside table, another in the end table near the couch, one on my home office desk and another on my desk at work.

    -- Read more on ScientificAmerican.com
  • Tapping Your Inner Rain Man 21/07/2014 12:30
    A blow to the head can sometimes unmask hidden artistic or intellectual gifts

    -- Read more on ScientificAmerican.com
  • Adjunct Instructors Petition for Better Pay, Job Security 19/07/2014 03:23
    Note: We’re pleased to feature a guest post by former Cocktail Party Physics co-blogger Ann (Lee) Kottner. Jennifer has graciously given me space to ask for some help from the science writing...

    -- Read more on ScientificAmerican.com
  • Scientific American Editor Testifies at U.S. Senate [Video] 18/07/2014 05:17
    At a hearing on the future of federal research investment, a science magazine editor and three noted scientists asked the U.S. Senate to support basic research

    -- Read more on ScientificAmerican.com
  • Bioinformatics: Big Data Versus the Big C 11/07/2014 12:00
    The torrents of data flowing out of cancer research and treatment are yielding fresh insight into the disease

    -- Read more on ScientificAmerican.com
  • LEGO Reveals Female Scientist Minifigures 10/07/2014 16:55
    After much rejoicing at the news last month that LEGO would mass-produce a set of female scientist minifigures, the company has released a prototype of the final set to its original designer, Ellen...

    -- Read more on ScientificAmerican.com
  • Some Infinities Are Bigger than Other Infinities, and Some Are Just the Same Size 10/07/2014 12:00
    Warning: contains minor spoilers for The Fault in Our Stars. I recently read The Fault in Our Stars by John Green, now a major motion picture that has led to theft in Amsterdam and a shortage of...

    -- Read more on ScientificAmerican.com
  • Put Yourself in the Cheater's Shoes 09/07/2014 20:17
    Could seeing the world through the eyes of the scientist who behaves unethically be a valuable tool for those trying to behave ethically? Last semester, I asked my “Ethics in Science”...

    -- Read more on ScientificAmerican.com
  • The Magic of Number 9 (Part 2) 09/07/2014 12:15
    The number 9 is kind of amazing. How amazing? Keep on reading for the exciting conclusion to Math Dude's story about the magical number 9 

    -- Read more on ScientificAmerican.com