How To Knit A Scrunchie Onto A Hair Tie - plus a little knitting chat - YouTube
How To Knit A Scrunchy 3 Ways! – The Snugglery
I wrote a free pattern for a scrunchie knitted either with 2mm, 3mm or 4mm double pointed needles and some yarn leftovers. You can find the pattern on ravelry (link in comments)