There are websites online which show how to convert flat knitting to circular knitting like this one here. And I can certainly use stitch patterns found in patterns for items like socks and mittens. Two good suggestions I've had are to use the stitch patterns in Charlene Schurch's sock books-- Sensational Knitted Socks and More Sensational Knitted Socks. I'll be getting copies of these books from my library next week.
What I'd really like is a dictionary for circular knit patterns. I heard there's one being published this month Up, Down, All Around Stitch Dictionary: More than 150 Stitch Patterns to Knit Top Down, Bottom Up, Back and Forth, and in the Round by Wendy Bernard which is a start. I've asked my library to purchase a copy and I hope that they do.