Find My iPad - http://www.apple.com/ipad/find-my-ipad.html - has to be enabled before device is lost. It also requires the device be on and connected to registered WiFi network or data service, and not having been restored by the finder (if it was really stolen then the thief has probably restored it). If you have activated the "Find My" feature, go to https://www.icloud.com or use the Find My iPhone app - http://itunes.apple.com/us/app/find-my-iphone/id376101648?mt=8
Setting up iCloud (requires iOS5) - http://www.apple.com/icloud/setup/ios.html - includes activating the 'Find My' feature.
Reporting a lost or stolen Apple product - http://support.apple.com/kb/ht2526 - "... Apple does not have a process to track or flag lost or stolen product..."
Change passwords on any accounts you use through the iPad. Notify the police of the theft.
These links may be helpful.
How to Track and Report Stolen iPad
Reporting a lost or stolen Apple product
Report Stolen iPad Tips and iPad Theft Prevention
How to recover a lost or stolen iPad
How to Find a Stolen iPad
Apple Product Lost or Stolen
Oops! iForgot My New iPad On the Plane; Now What?
If you don't know your lost/stolen iPad's serial number, use the instructions below.
How to Find Your iPad Serial Number
Unfortunately, even with find my ipad the app only works if the iPad is online somehow, either through 3/4G or wifi. ALso a 'good' thief can disable it within minutes. Find really works more as a 'where did i sit it down' than a theft recovery app.
As to protecting your iTunes. change the password. now. you can also go in and, i believe, temporarily, remove your credit card from the account.
As mentioned, you'll also want to change any password you've ever entered into that device. e-mail or websites etc.
Chances are the thief stole the device to wipe the device and resell it or use it him/herself. but you can't be too careful.
thank you very much for replies! i wonder, how can i block/delete my credit card information. im logged off from my apple id on this iPad so there is a small chance they'd try to hack it or smth. I live almost in Africa - Canary Islands, Spain. So.. people mostly steal to sell and buy drugs etc.
anyways, in a bank support I've been told to block a credit card. I don't want to block it and would like to block my Apple id instead. Is it possible? Thank you!