Cell Phone Number Locator?

  Today morning I lost my cell phone, and I do not remember exactly where I missed it. I tried to call on my cell phone, its ringing but no one is picking the cell phone. I am unable to find out that any one has stolen it or I myself have forgotten by keeping it some where.  Anyways,  now I want any one of you to suggest me some good cell phone number locator through which I can find out my cell phone. I have tried with free version on net but did not get any satisfactory answer. You can also provide me  with some links on internet if possible.