Any business that sells awards or certificates online is a safe bet for finding free printable borders. Such businesses will almost always offer a certain number of no-charge downloadable samples of their products, and if you only need free printable borders for a smaller number of projects, this might be your best bet.
Dedicated sites with content solely about free printable borders are some of the best resources you'll find. These are basically everywhere you turn and allow users to have access to their entire collection of borders without forking over a cent. People publishing sites like this do so just because they want to help others and are passionate about design and graphics.
Searching teacher supply websites can usually produce a number of free printable borders. Teacher supply sites often offer numerous downloads available as a courtesy to them for being educators, making these absolutely worthwhile spots to look.
Any software used for designing or publishing should have a number of free printable borders bundled with it. You can find programs like that in demo versions all over the Web. Sometimes they come packaged inside a program you may have already purchased, or you can download them from many companies and developers online.