I don't know if I am preaching to the already converted, but I have been using a fantastic website for FREE photo reference pics for ages now. It is www.flickr.com
There are literally thousands upon thousands of photos, just type in your required subject and it will most likely be there. Some pics cannot be downloaded, but most can, and they come in a range of sizes. So if you haven't explored this site yet I suggest you do so real soon, it's GREAT.
I also store my photos in a programme called iPhoto on my computer, and just print them out as and when I need to.
Hope this helps someone, happy hunting.