Did you try the hammer? Mine died the other way, ie: it wouldn't spin, just died. First it was slow starting and eventually it just quit. It was as if the battery was dead, no clicking.
It took me quite a few taps with the hammer but I got it running again and back to my garage for a swap (most starters are fairly easy to replace, just a couple of bolts).
I had an old CJ7 where the starter would die and I had to routinely crawler underneath and give 'er a good ol' tap with a rock to get going again.
Now if you get the low-battery clicking sound, it could also be the wires (as mentioned). Especially if grime/grease has gotten around your motor. You can clean these up and see if it clears (this is usually what gets Discoveries, due to the starters location, but I wasn't so lucky). If you do this, note that the solenoid leads are usually next to each other and also usually hot. You can get quite the spark display if you happen to short them! Disconnect the battery first..