Today when I drove to work everything was working good, but when I finished work, started my car, pushed in the clutch, and tried to put it in reverse all I got was a grinding noise..grrrrrrrr...and it wouldn't go into any gear at all.
My clutch is hydraulic  and yes there is fluid and it is working because I looked under the car while someone pushed on the clutch.
What could have broke?  The clutch wasn't slipping and it went into all the gears just fine before it broke...well at least its close enough to push it to the service station where they will charge me an arm and a leg to fix.

Since you said the slave cylinder was in good working condition, It could be a few other things, a bent or broken clutch fork, a bad throwout bearing, or it could just be time for a new clutch(which I don't think it is b/c there would have signs that the clutch was wearing down). When you say you looked under the car i was assuming you meant you were looking at the slave, was it giving full stroke, it should push the fork a good 3/4-1" .  anything less would cause bad clutch engagement.  Hope this helps.................

Everything seems to be working fine now.   I don't know what the problem was?  Maybe I should change the fluid..