Computing Minimal Equal Sums Of Like Powers:Jean-Charles Meyrignac's distributed-computing project on equal sums of like powers and the place to look for the current status of the problem.
Equal Sums of Like Powers:Chen Shuwen's extensive collection of equal sums of like powers, especially those that are solutions to multigrade equations.
Equations Involving Sums of Powers: Joseph McLean's investigations into those equations.
On Equal Sums of Like Powers and Related Problems: Classification of problems related to equal sums of like powers.
Overview of Mathematician Secret Room: Page keeping track of solutions of x^3+y^3+z^3 < 1000 and x^3+y^3+2*z^3 < 1000.
Power Page: Steve Dutch's page about powers of numbers.
Sortedsums: D. J. Bernstein's collection of tools for enumerating small solutions to certain types of equal sums of like powers.
Taxicab Numbers: David W. Wilson's list of the smallest number that can be expressed as a sum of two positive cubes in n different ways, for n = 1 through 5.
The Fifth Taxicab Number is 48988659276962496: David W. Wilson's article on his search for the smallest integer that can be expressed as a sum of two positive cubes in 5 distinct ways, up to order of summands.
Tom's Mathematical Things: Dissertation about equal sums of like powers by Tom Womack.