I enjoy working from print resources most, but buying anatomy books, artist gallery books, ect. can get expensive. purchasing magazines is a good way to collect fashion and clothing reference. you can find a photography book or magazine for just about any subject.
Internet and Digital reference seems easier to come by, however. between 3DSK, free samples from websites, fashion sites, flikr, stock photo sites and the entirety of the internet, this seems the most simple path. I tend to clump these into general catagories, then I tag them in Windows Picture viewer for easier searching.
My question is this, What have you found to be the most fruitful method of collecting reference?