This has probably been raised before, apologies for re-plugging it, I've been away for a year working on said site.
There are over 2000 proofs and 1200 definitions up now, but it needs a lot of work to lay down much of the groundwork in (particularly) prob&stats, applied maths and graph theory, to mention but a very few.
Plus, if anyone's a wizard at mathematical logic, you may want to pick up on where the poor author left off through lack of remaining brain cells at establishing some of the basic truths of predicate calculus.
ProofWiki