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
Summoning
From Diablo 2 Wiki
Both the Druid and the Necromancer have summoning skill trees. Click their names to select the one you wish to view.
