It sounds like you need a clutch master cylinder or slave cylinder. Its a hydraulic clutch and it works very much like your brakes. When you push the clutch in, a piston in the master cylinder pushes fluid through a hose. That fluid pushes a piston in the slave cylinder which disengages the clutch. Old clutches were mechanical, and although they were reliable, they were a packaging nightmare.
What happens in your situation is one of the pistons (in either the master cylinder or the slave cylinder) loses a seal and leaks fluid. When you push the pedal down, it doesn't transfer motion to the clutch as well because the fluid leaks past the piston seals.
That's my guess, but I'm sure someone with more clutch expertise will come in and clear things up
