I still play the game. As a matter of fact I will be playing this game today.
What they are worth depends on what set they are from. Some sets like the primary edition or so easily found that they are not worth the cardboard they are on (save for some of the very rares). Other sets are so hard to find that you have to be extremely lucky to even find them let alone get someone who might still be playing to sell/trade them.
Unfortunately there is no easy way to tell what set a card is from nor what their rarity is as neither is printed on the card.