I steal mine from work (not kidding)
I work at a telephone co, and we also do PC work so Ive got literally endless supplies of wire of all sorts, as well as connecters and the like
If youre using cat-5, you might do better with patch cords as opposed to bulk boxes. Patch cords are designed to be flexible, some use stranded wire. THe bulk stuff is generally intended to be run and left alone in the walls