Cut The Knot!

KöMaL

Final Answers on Numericana
by Dr. Michon.

Many basic and advanced scientific questions answered within days.
Ask Gerard any question.  Some answers are posted here.

The Mathematical Tourist, by Ivars Peterson
Devlin's Angle, by Keith Devlin
Card Colm, by Colm Mulcahy
Launchings, by David Bressoud
Math Games, by Ed Pegg, Jr.
How Euler Did It, by Ed Sandifer
Math Chat, by Frank Morgan
Cut the Knot, by Alex Bogomolny
MathTrek, By Ivars Peterson

Solvers

Helpful Internet Computing Websites

quickmath.com uses Mathematica to solve, simplify, and graph,
and so does   -- Here are some tips for using Wolfram's Integrator from David Loeffler:

With a bit of ingenuity you can use Wolfram's integrator for definite integrals too. If you embed a definite integral inside a vacuous indefinite integral, it will evaluate the definite integral first.  For example if you enter Integrate[Exp[-y^2], {y,0,Infinity}] into the box, it will try and evaluate

and return x times the value of the integral in the middle, which is just 1/2 Öp.  You can put any expression you like, not necessarily an integral, inside: feed it Sum[1/(n^2 + a^2),{n,0,Infinity}], for example. Just as long as what you're giving it doesn't involve x, you're fine.

Prime Factorization Machine does just what it says.
Dario Alpern's page, Factorization using the Elliptic Curve Method does it faster!
Inverse Symbolic Calculator turns a number into the formula that generated that number! 
  Plouffe's Inverter also turns a number into the formula that generated that number!
Fibonacci Calculator gives exact values of Fibonacci Numbers, Lucas Numbers, and "Rabbit" numbers. (linked from here)

Letter Puzzle Solvers

The Cryptarithmetic Puzzle Solver solves problems like LIP+LIP=KISS and THREE+THREE+F0UR=ELEVEN

The Alphametic Puzzle Solver also solves such problems

NRICH.maths.org/  (part of the Millennium Mathematics Project)-- click "Links" to get hundreds of categorized links

  Math Forum Internet News is a newsletter with links to all sorts of math resources

Five Numbers (Zero, Pi, Phi, i, and infinity) -- click the link at the bottom of this page to hear the program (originally broadcast in March, 2002, on BBC Radio4) in Real Audio format.

SAT preparation and more
Mathactive.com -- test preparation, tutoring, and distance learning for mathematics
NRICH.maths.org/ -- click "ask NRICH" to access the web board
mcraefamily.com/MathHelp/ is Graeme's math website
algebra.com is yet another homework-solving mathboard
purplemath.com is a resource for algebra students
mnemo.nu  a brand new (as of 9/27/2002) discussion board website from some foreign country
www.mathematics.0catch.com/ asks for a donation in return for help with math or physics homework
www.cms.livjm.ac.uk/cmsjkung/index11.htm is an experimental Java-based math tutor.
www.hotmath.org provides free solutions for actual math homework problems in many popular algebra, geometry, and calculus textbooks
physicsforums.com has a number of free forums, including one on mathematics.

Anne Bell's Recommendations

www.cia.gov/cia/ciakids/codegame/index.html -- Break the secret code
http://mathforum.org/alejandre/magic.star -- Like a magic square, except it's a star
www.aplusmath.com/games/index.html -- Flashcards, worksheets, java programs
www.nottingham.ac.uk/education/number -- Fun facts about the number of today's date
www.cookwithlyle.co.uk -- A shockwave-enhanced resource for kids
www.bbc.co.uk/education/schools/digger -- English, Math, and Science for kids up to age 11
www.cadburylearningzone.co.uk/maths/index_content.htm  -- math for kids
www.funbrain.com/ofm/index.html -- escape the haunted house by solving math puzzles
www.learningplanet.com/sam/ff/index.asp -- shockwave-enhanced Fraction Frenzy
www.mathscats.com/explore/multiplicationtable.html -- not found on 6/16/2002
www.funbrain.com/linejump/index.html -- arithmetic facts using a number line 

Links to several dozen problem-solving methods including 3D Plotting Tool, Bar Graph, Brownian Motion Simulator, Bull's-Eye Shot, Calculator, Computing a Summation, Curve Fit, Definite Integrals, Diffusion Simulator, Elastic collision, Elastic collision (2:1 ratio), Factoring a Polynomial, Gas under a piston, Grade Manager, Implicit Differentiation, Integration, Kepler's laws, Laboratory Report Writer, Limits, Limits & Derivative Tools, Multiplication Table, Osmosis Simulator, Pie Graph, Polynomial Addition, Polynomial Multiplication, Projectile motion, Regression Analysis, Solar system, Solids of Revolution, Solving a System of Equations, Solving a Polynomial Equation, Tangent Lines, and Weight & Measure

Java-based visualization aids

http://www.thesaurus.maths.org/dictionary/map/word/2098 -- The first Napoleon Point

http://math2.math.nthu.edu.tw/jcchuan/java-sketchpad/jsp.html -- A smorgasbord of java applets for visualizing all sorts of geometric factoids