Hi,
I just happened upon Google Books. They have scanned in thousands of fly fishing books and are searchable on the web:
http://books.google.com/books?client=firefox-a&um=1&ct=property-revision&lr=&q=%22fly+fishing%22&ie=ISO-8859-1&as_brr=3
The books out of copyright are in full text. Books in copyright are "limited preview" which appears in many cases to be ommission of 10-20% of the pages at random.
I just killed an hour scanning fly patterns from books 100 years ago. Now to get tying some cow dung flies.
John