If you had the Android Device Manager enabled on the device, you should be able to track its location (and optionally lock or wipe the device) from the web at https://www.google.com/android/devicemanager
Alternatively, you may be able to install the Plan B
app from the Google Play Store website and get it to report a location.
If neither of these work, your best bet may be to contact the local police and your carrier. Be sure to change the passwords for any accounts that you may have connected with the device!