Margaret Beaufort, mother of Henry VII
Here are a few useful family tree databases that I've found online. Most of these are regularly updated, and, unlike your typical family tree published online, these are actually SOURCED!
Ancestors of Paul Bailey McBride "Ancestors of Note," with bibliography, citations & index.
Banks-Dean Genealogy [Gordon Banks]. With tables, citations and index. Over 12,000 entries.
The Ancestry of Elizabeth FitzAlan & Her Sister Joan [John Blythe Dobson]. Tables with sources.