The D.U.C.K.man, a website created by Sigvald Grøsfjeld jr. and dedicated to Donald Duck illustrator Don Rosa, has a neat scan of the Donald Duck Family Tree.
If you've ever wanted to know how Scrooge McDuck is related to "Dirty" Dingus McDuck, here's your chance: http://duckman.pettho.com/tree/american.html - via AQFL
BTW, most Don Rosa comics have the letters D.U.C.K. (for Dedicated to Unca Carl from Keno) hidden somewhere in the first panel. This is because Disney does not allow personal signatures in the comics.