I saw a post on the Austin Permaculture group through Yahoo a mention of scribd.com as a free source of permaculture info. I checked it out and was able to download for free a number of books/articles/how-to guides, some quite lengthy.
There is a free sign up and then I typed permaculture into the search box and there popped up a lot of choices. I downloaded 5 or 6. There are a few that you cannot download but you can always read for free on the website.
There are, of course many other topics covered here, too, but this fits our needs very well.