If you seriously want to box you need acess to a ring, sparring partners and above all things a real trainer:
http://www.boxinggyms.com/addressbook.htm
http://www.boxinggyms.com/findgoodgym.htm[/b]
Alternatively I recommend asking around in local gyms and sports shops, they often get given numbers from clubs just incase some one like you asks for a gym 
comprehensive list for Canada, by province associations.
Provincial Association - About Us - Boxing Canada
list for Ontario, by club and contacts.
anyone has links they want to add, for your country or area, please go ahead.
thanks.
Not solely boxing gyms but Gym Visit is very comprehensive Google Gym Visit
You can find gym area near your home from mobile.