Check the external things first before removing the tranny and checking the clutch disk itself. For example, check the clutch cable mounting point at the firewall to be sure it's not broken, and also, check the clutch pedal pivot point to be sure it's not broken. Also, try adjusting the cable at the tranny.

If it's not what i said, it is more than likely a broken clutch disk spring like posted above, which will require dropping the tranny and replacing the clutch disk ,pressure plate, throwout and pilot bearing. A clutch kit can be bought for around 150 bucks. It's the labor that will cost you if you can't do it yourself.