I have the IP of the person who hacked my site.what do I do now.

DO a "whois" search on it. This can give you the relative location of the IP and the ISP it came from. You should then contact that ISP anf give them the information. Also, give it to law enforcement.
Keep in mind the IP that you turned up may not be the source of the hacker, it could have been spoofed or run through a proxie.

Hey,

If you have got the IP then, go and find out the exact location and get things confirmed who actually hacked in your account. There may be a possibility that the actual hacker has hacked some other IP and then attacked on your account, so do take such things into consideration and then take legal action accordingly.

All the best!!!!

The hackers will not do their hacking attempt from their own connectivity in most of the cases. Even if we know that the IP address is their own, there are less possibility for us to punish them. It need log of effort to find them and punish them. If the hacker is from your own country, then there will not be much problem in doing so. If they are from other countries, then we need to face various issues. Better have the precautionary measures to prevent hacking. I feel prevention is better than cure. Because, practically we may not be able to face or pressurize the others to take action or punish the concerned person, as we are individual. But we can do, if we strictly want to do.

Well, if you are barely expiencede dealing with hackers, IP address is pretty much useless, as it is basically public stuff. YOu can easily find my IP, and I can find yours. Now, the problem is tracking him down.

From the replies of this post, I would think you can't do anything about it. The hacker most probably have used a proxy, if so, there is actually no clear method of getting him. What to do now? Nothing I suppose. Still, the best defense is to keep your site hacker-safe.