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

— New: Trading – Post your loot!

— 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