Can I play too
I haven't focused much on agression but mostly on all over dog training theory and language.
My favourites for general stuff:
Anything Patricia McConnell (For Love of a Dog, The Other End of the Leash, Feisty Fido, Puppy Primer and many booklets). I agree with LP that her seminar is wonderful and I do have one of her DVD's here to watch as well.
Suzanne Clothier - Bones Would Rain from the sky
I also love the Turid Rugas - On Talking Term With Dogs - Calming Signals and the Brenda Aloff book Canine Body Language
Jean Donaldson - Culture Clash
For more training style:
I loved Gail Fisher - The Thinking Dog - Crossover to Clicker Training
Karen Pryor - Reaching the Animal Mind
Leslie McDervitt - Control Unleashed (and DVD)
Karen Pryor - Clicker training for dogs (very general but good intro) also Don't Shoot the Dog
Susan Garrett - Shaping Success