Bibliography on Hilbert's Tenth Problem  
   Searchable, ~400 items.
   http://liinwww.ira.uka.de/bibliography/Math/Hilbert10.html

Diophantine Equations  
   Dave Rusin's guide to Diophantine equations.
   http://www.math.niu.edu/~rusin/papers/known-math/index/11DXX.html

Egyptian Fractions  
   Lots of information about Egyptian fractions collected by David Eppstein.
   http://www.ics.uci.edu/~eppstein/numth/egypt/

The Erdos-Strauss Conjecture  
   The conjecture states that for any integer n > 1 there are integers a, b, and c with 4/n = 1/a + 1/b + 1/c, a > 0, b > 0, c > 0. The page establishes that the conjecture is true for all integers n, 1 < n <= 10^14. Tables and software by
   http://math.uindy.edu/swett/esc.htm

Developing A General 2nd Degree Diophantine Equation x^2 + p = 2^n  
   Methods to solve these equations.
   http://www.biochem.okstate.edu/OAS/OJAS/thiendo.htm

Thue Equations  
   Definition of the problem and a list of special cases that have been solved, by Clemens Heuberger.
   http://finanz.math.tu-graz.ac.at/~cheub/thue.html

Diophantine Geometry in Characteristic p  
   A survey by José Felipe Voloch.
   http://www.ma.utexas.edu/users/voloch/surveylatex/surveylatex.html

Pythagorean Triplets  
   A Javascript calculator for pythagorean triplets.
   http://www.faust.fr.bw.schule.de/mhb/pythagen.htm

Hilbert's Tenth Problem  
   Given a Diophantine equation with any number of unknowns and with rational integer coefficients: devise a process, which could determine by a finite number of operations whether the equation is solvable in rational integers.
   http://www.ltn.lv/~podnieks/gt4.html

Quadratic Diophantine Equation Solver  
   Dario Alpern's Java/JavaScript code that solves Diophantine equations of the form Ax^2 + Bxy + Cy^2 + Dx + Ey + F = 0 in two selectable modes: "solution only" and "step by step" (or "teach") mode. There is also a link to his
   http://www.alpertron.com.ar/QUAD.HTM

Pythagorean Triples in JAVA  
   A JavaScript applet which reads a and gives integer solutions of a^2+b^2 = c^2.
   http://home.foni.net/~heinzbecker/pythagoras.html

Diophantine m-tuples  
   Sets with the property that the product of any two distinct elements is one less than a square. Notes and bibliography by Andrej Dujella.
   http://www.math.hr/~duje/dtuples.html

Rational Triangles  
   Triangles in the Euclidean plane such that all three sides are rational. With tables of Heronian and Pythagorean triples.
   http://grail.cba.csuohio.edu/~somos/rattri.html

On the Psixyology of Diophantine Equations  
   PhD thesis, Pieter Moree, Leiden, 1993.
   http://web.inter.NL.net/hcc/J.Moree/linkind2.htm

Solving General Pell Equations  
   John Robertson's treatise on how to solve Diophantine equations of the form x^2 - dy^2 = N.
   http://hometown.aol.com/jpr2718/pelleqns.html

Pell's Equation  
   Record solutions.
   http://www.ieeta.pt/~tos/pell.html

Fermat's Method of Infinite Descent  
   Notes by Jamie Bailey and Brian Oberg. Illustrates the method on FLT with exponent 4.
   http://sweb.uky.edu/~jrbail01/fermat.htm

Diophantus Quadraticus  
   On-line Pell Equation solver by Michael Zuker.
   http://www.bioinfo.rpi.edu/~zukerm/cgi-bin/dq.html

Rational and Integral Points on Higher-dimensional Varieties  
   Some of conjectures and open problems, compiled at AIM.
   http://aimath.org/WWN/qptsurface2/

1, 3, 8, 120, ...  
   Sets of numbers such that the product of any two is one less than a square. Diophantus found the rational set 1/16, 33/16, 17/4, 105/16; Fermat the integer set 1, 3, 8, 120.
   http://www.weburbia.demon.co.uk/pg/diophant.htm

MAGMA program  
   MAGMA code to solve Diophantine equations of the form F(x)=G(y), for which Runge's condition is satisfied. Created by Szabolcs Tengely.
   http://www.math.leidenuniv.nl/~tengely/main2.html

Diagonal Quartic Surfaces  
   Articles, computations and software in Magma and GP by Martin Bright.
   http://www.boojum.org.uk/maths/quartic-surfaces/

Linear Diophantine Equations  
   A web tool for solving Diophantine equations of the form ax + by = c.
   http://www.thoralf.uwaterloo.ca/htdocs/linear.html