Self-serving links, forgive me, but I think (hope) they really ARE useful, and they're very new and shiny:
ScoutingBook Prospect Ranks (not just once per year; updated near-daily)
ScoutingBook Closer Watch (also updated daily)
Those are most useful at draft time, of course. There are some new 'management' tools coming in April to help with roster-making and waiver scrounging, too, but I think they're still being tested.