Clutch Slave Cylinder
Ok, these are known to wear out. Pretty common and not hard to replace. The symptom I had (apparently common) is that the clutch pedal magically acted like it was out of adjustment but I hadn't touched it. I had to push the pedal to the floor to get it to disengage. It got so bad that the floor wasn't far enough. Once I got under the car, it was apparent that the slave cylinder was leaking. A squeeze of the rubber boot and fluid came pouring out.
I HIGHLY recommend that if you have a failure with the slave cylinder, just replace the whole thing instead of rebuilding it. They are cheap and aren't worth the potential malfunction of a do-it-yourself rebuilt one. However, here are some pics of how one could be rebuilt. I had a spare rebuild kit so I gave it a shot. The piston ended up getting hung up within the cylinder. The cylinder apparently is not real smooth anymore. Oh well, good for pictures, right?
Here is the original slave cylinder with the pushrod and boot removed.
You can see the piston inside (shiny part) poking out like a turtle head (Austin Powers reference). ;-)
The original piston is on the left, the new one (part of the do-it-yourself rebuild kit) is on the right. Notice the black seal on the pistons? This is what wears out and causes the failure. The spring helps push the piston back into proper position.
Here is the new cylinder next to the old cylinder. Note that even on the new cylinder, you have to transfer the push rod over from the old cylinder. Don't worry, this doesn't seem to be a wear sensitive component. It's really a very easy install.