I read the blog Wise Bread: living large on a small budget and saw a post there today on how to be a cheap reader. I tend to prefer hard copies of books. I like to prop up in bed and turn the pages of a used book, so I haunt the local used book stores to feed my passion. If I did want to read books from a computer screen, though, Wise Bread has a link to a site that has links to travel narratives online: Explorion. There are wonderful things there! They have Dickens' Pictures From Italy, Powell's Canyons of the Cororado, Henry James' Italian Hours, Mungo Park's Travels In Central Africa, Isabella Bird's Among the Tibetans, Francis Parkman's The Oregon Trail, William Bartram's Travels, Kinglake's Eothen, Stanley's How I Found Livingstone, The Journals of Lewis and Clark, The Itinerary of Benjamin of Tudela (which led me a merry chase before I finally gave up finding a hard copy), Burton's Personal Narrative of a Pilgrimage to Al-Madinah and Meccah, Mary Kingsley's Travels in West Africa and just entirely too many others to mention.
I have hard copies of some of the books listed on this site but nowhere near all, and I'm inspired to seek some out that I've never paid much attention to before.
There is a wikipedia article here which contains some general information about this literary genre, including a list of notable works. Longitude Books has a great selection and has sections on "Neglected Classics" and "Favorites" and has book recommendations divided by region.