IV) 1) The International Obfuscated C Code Contest
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http://www.ioccc.org/   (dmoz)

IV) 2) Programming Contest Problems Archive
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http://www.inf.bme.hu/contests/tasks/   (dmoz)

IV) 3) iPhotoContest
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http://www.iphotocontest.com/   (dmoz)

IV) 4) Internet Problem Solving Contest
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http://ipsc.ksp.sk/   (dmoz)

IV) 5) Field and Forest Photo Contest
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http://www.fieldandforest.com/contest/contestrules.html   (dmoz)

IV) 6) Eurovision Song Contest
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http://www.eurovision.tv/   (dmoz)

IV) 7) Daily Awards Photography Contests
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http://www.dailyawards.com/   (dmoz)

IV) 8) Bart's Contest
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http://bartscontest.com   (dmoz)

IV) 9) Annual Berkeley Programming Contest
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http://www.cs.berkeley.edu/~hilfingr/programming-contest/   (dmoz)

IV) 10) Al Zimmermann's Programming Contests
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http://www.recmath.org/Contest   (dmoz)