Here are some links to sites and books we have found useful:

Goodbirdinc A site with great resources for your birds, including books, dvd's and toys. Barbara Heidenreich is a very experienced bird behaviourist. She even spent some time with NZ's famous kakapo, Sirocco.
Cockatiel Cottage A great site with a wealth of information about cockatiels
Australian Cockatiel Society A great resource site
Petbus A company that will transport birds (and other pets) within New Zealand
North American Cockatiel Society Lots of information about cockatiels
Tailfeathers A chat forum where you can discuss birds with like minded people
Natureland Zoo Our local zoo

Books we recommend

Cinnamon Chick 8 wks