Stitchfiddle (Facebook) (Instagram) (Ravelry) (Twitter) is a website that lets you create the charts that exist with knitting patterns. It’s mostly for designers, but I’ve used it to create charts for patterns with written instructions.
If you log in, you can save a max of 15 charts. With Premium, you can make charts without a “Designed with stitchfiddle” watermark.
It works for both simple charts and more advanced charts for multiple colors, brioche, lace, cables, and mosaic. Below are two examples of charts that I’ve made – the left is a mosaic chart and the right is a cable chart.