Q: I can't find my ipod touch in the house. I don't have the serial number.

Find My iPod had to be activated on your device before you lost it in order to locate it using Find My iPhone on icloud.com.  But even if you did, the location accuracy isn't going to show you where it is inside your house, it would only show you that it at your home address (at best).

Having the serial number isn't going to help you locate it, but if you've ever backed it up in iTunes you can go to iTunes>Preferences>Devices and hover your mouse over the name of your backup to get a pop-up showing you the serial number.