Is the any way to find my stolen Mac? Two weeks ago, my 13" Macbook Pro was stolen. Is there any way to locate my laptop if and when the thief accesses the internet?

Is there any application or a website similar to this that can give me an alert message if I register my Macbook pro ID number?
It depends. If your machine was password protected, you might be out of luck. If not, there are a few possibilities.

If you have SSH enabled that might be an option. Also, if you had any remote access programs installed, like TeamViewer or LogMeIn, you have a chance to find it, assuming it's connected to the internet.

Regardless, I suggest contacting Apple and telling them the serial number of the machine and that it was stolen. If it's brought in for service, you might be able to get it back. (Although Apple has no official policy on this, it doesn't hurt to tell them. I contacted them when my iMac was stolen. Like I said, not much help, but it's better than nothing.)

PS: Check this out. You might find it inspiring at least.