http://www.mt-whitney.info/viewtopic.php?p=3155

"The first shortcut, the original trailhead, is easiest to find: Walk past the Whitney Portal Store 
to the end of the paved road. Just before it loops to the left, to go to the picnic area, you will 
see a giant boulder on the right. On the far side of that boulder is the trail, otherwise unmarked. 
The trail is every bit as good as the current trail and shaves off quite a few minutes. It joins the 
current trail a few feet before the John Muir Wilderness sign.

Bob said the second shortcut I mentioned could be found about half a mile past the sign. I failed to 
spot it.

The third shortcut begins about fifty feet past the log bridge. If you look to the right, you will 
see the forest duff has been depressed by footprints. There isn't a developed trail there but an 
"implicit" one. Even if you miss where others have stepped, it's easy to go the right way because 
you're going up a narrow draw, with a roaring creek to your right and a rock wall to your left. Just 
stay between them--mostly to the left--until you top out at the east end of Bighorn Park, right where 
the main trail drops down from a switchback. At two or three spots you'll need to do a little rock 
scrambling--steadying yourself with your hands.

The fourth shortcut, at Trailside Meadow, I could not be sure of because of the snow bank where I believe 
the path goes. I was trying to work off a photo Bob had uploaded. The photo looked not outward from 
Trailside Meadow but back at the rock wall that is to your right as you go up the main trail there. I 
used the features of the wall to estimate where the shortcut began.

The fifth was at the summit, just where the main trail turns left to whip around the west side of the 
peak. It was easy to spot the start of the shortcut (it used to be the chief way up, I believe), because 
there is a bit of open ground there and obvious footprints, but I lost the trail several times on the 
ascent. Maybe I was scanning the sky too anxiously--this was the day of the bad thunderstorms, and I 
wanted to hightail it out of there if the clouds seemed to be developing into cu-nims, which they later 
did."