http://www.georgette-heyer.com/warren/ has genealogical charts for many of the novels
http://www.georgette-heyer.com/ has details of nearly all of the books, plus a complete short story, and a timeline for all the books.
http://heyerlist.org/slang.html has a nice set of slang but it's bellows to mend with me for it doesn't expand crim. con. I don't wish to cry rope on them and I suppose it's cream-pot love but they've steered my barque to Point Non Plus. I shall just have to go and read Cottilion again.