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
Bul-Kathos' Children: Difference between revisions
Partial set bonuses stack. If you are wearing three items, then you will get the bonus for wearing two items as well as the bonus for wearing three items. Full set bonuses stack on top of the partial bonuses, so if there is a partial bonus of +40 Life, and a full bonus of +40 Mana, with the complete set, you would receive both +40 life and +40 mana.