Empty vegetable oil jug refilled with water and placed on garbage can lid. Not as inconvenient as other possible items to weigh down the lid since it has a nifty handle. and so far Raven has not discovered how to lift this much weight!
Loop an elastic band around the handle of the drawer, pass through cupboard handle and loop back over drawer handle. Raven can pull the door open a centimetre or so. The door then snaps shut on him. Makes a little thumping noise, but that's it.
Voila! Low tech cat-proofing! With bonus points for cheapness.