We use Mask-Ease for most of our screen printing projects, but it's also possible to use printer transparency film to create reusable stencils. A transparency also offers the ability to use a copier or printer to directly transfer a design onto the film.
It can be tricky to work with since it doesn't have adhesive to hold it securely to the screen like the Mask-Ease, but with careful cutting and planning, it opens up a versatile (and more affordable) way to do screen printing.