I store mine in the plastic sleeves when I purchase the sheet sets. So far I have three because I have donated the patterns that I know I will never make, these three are seperated into Holidays, tablerunners, and baby quilts. ( the last, I devote most of my time making, so I have a large selection of these.)
Most of my baby quilt patterns have come off the internet, so I have a seperate folder for those.
CruisingStef