quoting Izambri, Duke, the Findible League:

quoting Rhetorica, Kelatetía:

Luciferous Logolepsy
"[A] collection of over 9,000 obscure English words."
Very much in the same vein as Phrontistery, this also emphasizes obscuranda.

Sadly, the domain expired. A charitable soul, though, has recollected many words from the site here.

Considering that this Wayback Machine archival copy says "over 9000" and arcane.org's mirror has 9034 words, I think it's probably safe to say the arcane.org version is comprehensive.

In a less obscure capacity, I went hunting for new words to add to the Lilitika corpus a week or two ago and came upon The Oxford 3000 and 5000, word lists that the ol' Anglo-Bosporus thinks are vital for fluency. This is pretty thrilling stuff in my opinion, as the 5000 list (which starts with word #3001 and goes to word #5000) is overflowing with a rich corpus of Latin verbs and subtle distinctions.

If you ever want to translate a book into a conlang (or, at least, an English book into a conlang) I think it is absolutely vital to have a vocabulary of this scale. There are obvious biases in the vocabulary—conspicuous inclusions on the second list like "visa," "expenditure," "asylum," "championship," "earnings," "portfolio," "resignation," "emission," and "columnist" evoke the life of petty London bourgeoisie when seen in context—but I just skipped over whatever was societally irrelevant, and avoided calquing Latin compound verbs that felt too unintuitive, instead seeking alternative derivations for the connotations of the modern English usage. Cleaned-up and de-duplicated versions can be found here: 3000, 5000, using the fancy wordlist comparison tech that still hasn't been rolled out to Annie1.