The independent Zion National Park website has added an attractive blog.
This endorsement by Bo for a slot canyon walk caught my eye:
Parunuweap Canyon “is my favorite hike of all times. After hiking just about everything in Zion and nearby and doing this one several times using different ways in and out, I can say without a doubt that Parunuweap is my favorite hike!”
High praise.
So much so that we’ve added Parunuweap to our list of the best hikes in North America.
I would recommend this hike to anyone who is fit!
Parunuweap, the south East fork of the Virgin river, is far, far less visited than much more famous Zion Narrows off the North fork.
Zion National Park – Wikipedia
larger version on flickr – WillsCreek
UPDATE:
Several hikers have written to say that access is not allowed for Parunuweap. Too bad.
UPDATE: Check the comments. Tim states: Actually, you’re allowed in through a technical route called “fat man’s misery.†The only reason the east fork is inaccessible is because of private land ownership on either side.
besthike.com 
Oh great, you say “Parunuweap, the south fork of the Virgin river, is far, far less visited than much more famous Zion Narrows”, so I look on the included map, and the south fork isn’t labeled?
OOPS.
I should have said the East Fork of the Virgin river, which happens to be south of the more famous Zion Narrows of the North Fork.
My bad.
Great looking Canyon!
We’ve finally got plans to visit Zion next year. Very excited about this!
DSD
a few years back, i was a student conservation association intern in ZIon and Last i Checked, parunuweap canyon was restricted to visit due in part to some archaeological artifacts that the park watnted to leave in tact.
if this isn’t the case then i stand corrected, but according to every single park ranger that i spoke with during my tenure said the same thing.
I was just at zion and that is exactly what I was told that there was no access allowed
Actually, you’re allowed in through a technical route called “fat man’s misery.” The only reason the east fork is inaccessible is because of private land ownership on either side.
Thanks Tim.
I updated the original post with your Misery comment.