For instance, I searched for a while for a nearly complete dictionary of English verbs and their corresponding conjugations. My friend entitled this a "declension-ary."
(a) Most dictionaries are also declension-aries,
(b) I really like your word declension-ary,
and (c) Declension is what you do to nouns and is analogous to conjugation of verbs, which I think is what you are looking for :-)
For people like us who need these things, but don't want to do it alone their should be a sort of Wikipedia/Digg like distributed lexical database.
Everyone contributes data as it's acquired, and it is then verified by the users with a simple up/down vote for each child node.
The data could even be automatically acquired, and just manually verified as it is utilized.
Still an overwhelming task, but I think it would be worth it given all the fields that overlap with Natural Language Processing these days.