Websites for Martha Stewart and Better Homes and Garden each offer many ideas for making birthday cards for free. The Saturday Evening Post has instructions for creating one birthday card.
DIY birthday card suggestions at Martha Stewart's site include using fabric paint, wallpaper scraps, yarn, family photos and pressed flowers. Each card has a link to step-by-step directions. On the Better Homes and Garden page, ideas include embroidered, computer-generated, stamped, card stock and lattice cards.
An article from the Saturday Evening Post provides a materials list and detailed directions for using bits of wrapping paper, scrap booking paper or old greeting cards to create an illustration of a layered cake topped by candles.