I recommend checking out Avialogs.com. They have thousands of manuals there, which can be downloaded for a nominal subscription fee that is equivalent to the purchase price of only a few manuals at the fee sites. The fee is used to fund the online service. I've personally downloaded a few hundred.
The manuals which were published by military services were prepared with public tax dollars. While I appreciate the service offered by for-profit manual providers, I believe that we have already paid for them once and government documents should be available to the public for the cost of providing them, nothing more. IMHO.