Tome of Diablo II (formerly Runeword Helper Pro) has everything you need to know about Diablo 2. Now updated for D2: Resurrected!

-- Runewords - searchable and filterable)
-- Runeword Calculator - Input the runes you have see what runewords you can or can almost make
-- Drop Calculator - calculate the exact chance of any item dropping
-- Attack Speed Calculator - Calculate exactly how much IAS you need to hit the breakpoints.
-- Run / Walk calculator
-- Area levels & Act maps
-- Mercenaries - Skills, Aura Levels, Level up Stats etc
-- Horadric Cube - Easily find that one cube recipe you can never quite remember
-- Breakpoints - FHR, FCR, FBR breakpoints for all classes and mercenaries
-- Item Catalog - Check the stats and bonuses on unique, set and base items.
-- Area Level - Check the area level for any area in the game.
-- Holy Grail - Keep track of all the items you've found and need to find for your Holy Grail quest

2.0.6

- Performance increases
- Drop Calculator bug fixes
- Drop Calculator results are now searchable
- Improvements to Holy Grail: Items can now be added/removed by clicking on the remaining/found numbers