A quick google search indicates that the mewtwo sells for two or three bucks non-foil, five bucks foil. A buyer interested in collecting movie promos might pay a bit more.
Dark Charmeleon is an uncommon, probably isn't worth much. Fearow might be worth a buck or so since it's a reverse holofoil.
Try google searching the card name and the set number at the bottom right corner. Reliable sellers include toywiz and trollandtoad.