Giovanni Resta wrote a very interesting article on his search for (6,2,5) (Giovanni Resta's article in PostScript format)
His source code is included !

http://www.mersenne.org
Lists all distributed computing projects (George Woltman)

http://www.pa.uky.edu/~childers/sums.html
Greg Childers page containing his Integer Relation program.
Greg Childers is the discoverer of the application of Integer Relation to the sum of powers problem.
He is also one of the main contributors to the equation (k,1,n) with k > 12 and he hosts the EulerNet server.

http://www.glasgowg43.freeserve.co.uk/sumintro.htm
Joe McLean's page. Independent search of equal sums of like powers.
Very interesting generalisations of the problem.
Definitely the page to start with if you want to have more explanations !

http://www.nease.net/~chin/eslp/
http://member.netease.com/~chin/eslp/eslp.htm
You can find a mirror of his page here.

http://www.spacefire.com/numbertheory/EqualSums.htm
Joe Crump's page
He and his brother (John Michael Crump) were the pioneers on high power search.

http://www.imc.pi.cnr.it/~resta/unlike.html
Giovanni Resta's page.
He wrote an interesting article about (6,2,5) which is the basis of EulerNet's search.

http://www.bearnol.pwp.blueyonder.co.uk/Math/index.html
James Wanless page, containing some Euler conjectures.

http://Tom.Womack.net/maths/maths.htm
Interesting work on (5,1,4) and some other diophantine equations.

http://www.rt66.com/~frye/euler88.ps
http://www.cybermesa.com/~rfrye/collab.htm
Roger Frye's article on how he found 958004+2175194+4145604=4224814 on the Connection Machine !

http://pobox.com/~djb/sortedsums.html
http://cr.yp.to/sortedsums.html
Interesting work on (4,1,3) and (3,2,2) (D.J. Bernstein)

http://arxiv.org/abs/math/0005139
Noam Elkies article how he computed |x^3+y^3-z^3| < M

Yasutoshi Kohmoto's parametrical equations on third power.

http://www.ams.org/jourcgi/amsjournal?fn=120&pg1=pii&s1=S002557189800979X
http://www.ams.org/jourcgi/amsjournal?fn=120&pg1=pii&s1=S0025571896007685
Lists some work on computing Equal Sums of Like Power

http://gutenberg.llnl.gov/~colvin/euler/
Massive computing effort on the problem

http://www.cs.man.ac.uk/cnc/EqualSums/
Another massive computing effort on the problem (Rizos Sakellariou)

http://www.mathsoft.com/asolve/fermat/fermat.html
Describes conditions on c so that the generalized Fermat-Wiles equation x^n+y^n=c*z^n has nontrivial integer solutions

http://listserv.nodak.edu/scripts/wa.exe?A2=ind9709&L=nmbrthry&D=0&P=1132
http://listserv.nodak.edu/scripts/wa.exe?A2=ind9709&L=nmbrthry&D=0&P=1037
http://listserv.nodak.edu/scripts/wa.exe?A2=ind9709&L=nmbrthry&P=R496
Some articles on the discovery of (4,1,3).

http://www.mathsoft.com/asolve/pwrs32/pwrs32.html
http://www.mathsoft.com/asolve/pwrs32/waring.html

http://www.math.niu.edu/~rusin/known-math/index/11PXX.html
Has some more references on the problem

http://users.ox.ac.uk/~mert0236/s253/
Computing exploration of a^5+b^5+c^5+d^5=e^5

This site has been designated a Cool Site in the Netscape Open Directory:
Science/Math/Number_Theory/Diophantine_Equations/Equal_Sums_of_Like_Powers
category at
http://dmoz.org/Science/Math/Number_Theory/Diophantine_Equations/Equal_Sums_of_Like_Powers/
(Thank you Warut Roonguthai !)

http://ksc9.th.com/warut/bookmarks.html
Warut Roonguthai's huge bookmark

http://www.asahi-net.or.jp/~KC2H-MSM/mathland/overview.htm
All solutions to x3+y3+z3 < 1000 and x3+y3+2*z3 < 1000

http://gbms01.uwgb.edu/~dutchs/recmath/rmpowers.htm
Various results about sums of powers.

http://arxiv.org/
http://www.researchindex.com/
Excellent for searching documents !

http://www.nonags.com/nonags/index.html
A huge list of Windows freeware sorted by category !

http://lottery.merseyworld.com/Wheel/
how much tickets are necessary to win on the english and french lotteries.

http://www.geocities.com/~harveyh
Harvey Heinz's collection of magic squares.

http://sodaplay.com/constructor/index.htm
A strange collection of organisms.

http://www.freewebspace.net
A huge list of free Internet services.

http://www.primepuzzles.net
Carlos Rivera's site about puzzles with primes.

http://www.faqs.org

http://www.yaromat.com/macos8/index.htm
An impressive demonstration of Mac System.

http://bridgebuilder.8m.com/
http://www.bridgebuilder.de/
Bridge Builder is an EXCELLENT optimization game, try it out !

http://www.theproduct.de/
Impressive 64K demo (yes, 65,536 bytes !!!)

http://www.256b.com/
Demos in 256 bytes (yes, bytes !)

REFERENCES

L.J. Lander, T.R. Parkin, J.L. Selfridge, A Survey of Equal Sums of Like Powers, Math. Comput. 21 (1967), pages 446-459.
R. Ekl, Equal Sums of Four Seventh Powers, Mathematics of Computation 65, number 216 (1996), pages 1755-1756.
Bob Scher, General Perfect Sums.