Maybe you could try contacting the Salvation Army or Covenant House; these 2 come to my mind as agencies who have "shelters" or missions.
Also, if you look in the Yellow Pages for your city under "Social Service Organizations" or "Charitable Organizations", this will tell you of other agencies operating in your area. If you call them, they could tell you more about themselves (and I am sure they would be happy to hear from you!)
Good luck!
