There are plenty of websites and groups of which we can recommend.  Here are a few that stand out.

recommended spay and neuter clinic

http://mashvet.net/

a great rescue group in colorado

 http://www.milldogrescue.org/index.html

 facts and myths on spay and neutering

http://www.hsus.org/pets/pet_care/why_you_should_spay_or_neuter_your_pet.html

free spays and neuters

http://www.maricopa.gov/pets/SpayNeuter/voucher.aspx

 pet adoption finder site

http://www.petfinder.com/

great general practice vet

http://gcahvet.com/

Trap and release groups-

www.thefoundationforhomelesscats.org 

Azcats 

http://www.alteredtails.org/TNR-ferals.html