is a great source for training books!

General Dog Training
The Power of Positive Dog Training, Pat Miller (dogwise) (amazon)
Culture Clash, Jean Donaldson (dogwise) (amazon)

Understanding Dogs
The Other End of the Leash, Patricia McConnell (dogwise) (amazon)
Bones Would Rain From the Sky, Suzanne Clothier (dogwise) (amazon)

Understanding Training
Don't Shoot the Dog!, Karen Pryor (dogwise) (amazon)
Excel-erated Learning, Pam Reid (dogwise) (amazon)

The Perfect Puppy, Gwen Bailey (dogwise) (amazon)
Taking Care of Puppy Business, Gail Pivar & Leslie Nelson (dogwise) (amazon)

Specific Issues
Way to Go!, Karen London & Patricia McConnell (dogwise) (amazon)
Separation Anxiety:
I'll Be Home Soon, Patricia McConnell (dogwise) (amazon)
Multi-Dog Households:
Feeling Outnumbered?, Karen London & Patricia McConnell (dogwise) (amazon)
Leash Aggression:
Feisty Fido, Patricia McConnell & Karen London (dogwise) (amazon)
Click to Calm, Emma Parsons (dogwise) (amazon)
Dog-dog aggression:
Fight!, Jean Donaldson (dogwise) (amazon)
Resource Guarding:
Mine, Jean Donaldso (dogwise) (amazon)

Canine Body Language
On Talking Terms with Dogs: Calming Signals, Turid Rugaas (dogwise) (amazon)
Canine Body Language: A Photographic Guide Interpreting the Native Language of the Domestic Dog, Brenda Aloff (dogwise) (amazon)
Dog Language: An Encyclopedia of Canine Behavior, Roger Abrantes (dogwise) (amazon)