While I'm on the subject of burgers, this Serious Eats article goes through the experimentation of different cuts of beef and different beef blends to figure out the best combo for a burger. I'm not sure how practical it is for the home-burger cook to grind up oxtail in particular, but certainly a great exploration and write-up nevertheless.
Also, Serious Eats' guide to hamburger & cheeseburger types.
The Mefi link, where I saw the original Serious Eats article, also has a bunch more burger-relevant links.
($Burgers / Hot Dogs, $Cooking)