English Spelling Statistics
Vivian Cook

One million words sample

Letter frequencies in English:
Single Letters  Digrams  Trigrams   Position in word

Contact chart for English letters

Punctuation mark frequencies in English

Carney's Consonant Letter to Sound Correspondences in English

Most of these were intended for the Routledge Handbook of the English Writing System (2016) but were felt to be insufficiently rigorous for print. While they are rough and ready, they provide some information not otherwise available.