Researching the famous walk in Spain, I started (as usual) with Wikipedia:
The Way of St. James or St. James’ Way, often known by its Spanish name, el Camino de Santiago, is the pilgrimage to the Cathedral of Santiago de Compostela in Galicia in northwestern Spain, where the remains of the apostle, Saint James the Great, are said to be buried.
The standard route — the Camino Francés (French Way) — is 800km route from Roncesvalles in the Pyrenees. But there are many variations starting as far away as France, Germany, and further afield.
(larger version – Regenisis.org.au)
I got interested in this walk, more religious pilgrimage than “best hike”, after reading an excerpt from a new book by Ward called All the Good Pilgrims : Tales of the Camino de Santiago.
Robert Ward has always enjoyed travelling, especially on foot. When he discovered the ancient pilgrimage route to Santiago in Spain, he felt compelled to walk and experience this historic road. From his first journey along the Camino de Santiago, Ward fell in love with the pace, landscape, history, art, and romance of this old pilgrimage path.
Above all, however, Ward fell in love with the people of the Camino—both the welcoming Spaniards and the pilgrims who come from all over the world to find out what it means to travel five hundred miles, one step at a time.
In All the Good Pilgrims, Ward returns to Spain to walk the Camino for the fifth time. He thinks he knows what he’s getting into but, as his many Camino journeys have taught him, the Camino never runs out of surprises. Each day brings new lessons, friendships, questions, memories, gifts and challenges, reminding Ward that it isn’t the pilgrim who walks the Camino—it’s the Camino that walks the pilgrim.
An engaging travel narrative, All the Good Pilgrims is a personal and insightful tour of the Camino de Santiago, as Ward takes readers on a secular pilgrimage in which he reflects on his past journeys and contemplates the mysterious and enduring allure of this ancient and historic road.
besthike.com 
Not exactly a backpack, but certainly qualifies as a grand adventure. About 50% of the walkers are doing it for religious purposes. Most of the others classify their purpose as spiritual, which covers a lot of ground. It is a demanding hike, just because of the day after day walking. We had just finished the John Muir Trail, a few weeks before we did the Camino, and still found it a challenge. We are now section hiking the Pacific Crest Trail, but still look back at the Camino as a life changing experience.
Wow.
I am looking at John Muir for August 2007. And would not have guessed that a pilgrimage would be as important to a serious hiker like yourself.
That’s it. I will add it to my “hike before I die list”.
Gracias.
Hi, I was pleased to see my book on your site. It’s true, the Camino is more of a long walk than a tough hike, but it’s not exactly a religious pilgrimage anymore, so much as a celebration of going slow and learning along the way. If anyone wants to see pictures of the Camino and get a better sense of what it’s all about, come and visit my new website, http://www.robertward.ca