The Diablo 2 Wiki
The Diablo 2 Wiki archive is available for anyone looking for information on Diablo 2. All information here is pre-D2R but contains a lot of useful information that is still relevant. Updated sections for new D2R features can be found on the PureDiablo Diablo 2 section

Category:Set Items

Category page
Diablo II Items [e]
Weapons
AxesBowsCrossbowsDaggersJavelinsMacesPolearmsSceptersSpearsStavesSwordsThrowingWands
Armor
BeltsBody ArmorBootsCircletsGlovesHelmsShields
Class-specific
Assassin ItemsAmazon ItemsBarbarian ItemsDruid ItemsNecromancer ItemsPaladin ItemsSorceress Items
Other
CharmsClass ItemsCraftedHoradric CubeRunesSet ItemsUniquesJewelsSockets
Guides and Stats
CalculationsGamblingItem GenerationModifiersRunewordsQuest ItemsPotionsEtherealGemsBase Item LevelsMisc

Set Items are collections of matched equipment that give special bonuses when worn together. Each item in the set has properties always found on that item. Wearing multiple items from the same set will give special "partial" set bonuses, and wearing the full set will give a still larger full set bonus.