You can take the old iPad to any Apple retail store for free recycling. Be sure to "Erase All Content and Settings" before handing it over. The store employees can assist you, but make sure you watch them do it.

You CANNOT throw an iPad (or any iOS device) in the trash because of the internal Lithium battery. It needs to be disposed of properly. If you are not able to recycle the device, contact your local department of public works to find out how to discard hazardous items like iOS devices containing Lithium batteries in your area.