It is important that you find an avian vet before your bird (s) become sick. When birds become sick they go downhill very quickly and if you don't have an avian vet that you know of you will go into panic mode. Be prepared! It may save your birds life.
USA/Canada:
http://aav.org/vet-lookup/
http://www.birdsnways.com/articles/abvpvets.htm
http://www.lafeber.com/FindALocal/Vet/default.aspx
Australia:
http://www.vetafarm.com.au/avian_vets.asp
UK/Other:
http://www.theparrotsocietyuk.org/avian-vets.shtml
http://www.parrotpassionsuk.com/Advice/Uk_Avian_Vets.htm