ENRICHING YOUR GAME WITH MAGIC:THE GATHERING CARDS
The obvious use is inspiration for monsters,that is where my "Smoke Teller" sub comes from(link below) But there are literally thousands of cards to pick from. They could even be used as a very cheep alternative in miniatures(trim the cards to just the illustartion) or to represent units on a large battlefield. Another great use is for spell effects, showing your players the actual visuals of what the BEMs spell looks like. Still another use is :The basic Land can be used to show the players where they are, non-basic lands can be very inspiring for specific locales.Commons and uncommons can often be purchased cheaply at FLGS and grab bags can be found online.
A VERY SANE way to play now that you have all these commons and uncommons
I build all the decks for my group and I have about 30 of them, this way you avoid power creep as everyone builds tougher more expensive decks,It also evens out the playing field by playing multiplayer, so the more powerful decks get stomped on.In a closed environment like this it's a great way to still play if your not up to DMing , tired or bored. You can also play "in character" or have the games represent battles or epic duels in continuity with your game world.
WARNING: IT CAN GET VERY ADDICTIVE AND SPENDING CAN GET OUT OF HAND, parental advisory is in effect.