Lots 'o cotton at the Scottish Weaver:

http://www.thescottishweaver.com/Cot...anPlaidFabric/

Also a few polycotton, polyacrylic and polyester:

http://www.thescottishweaver.com/Cot...anPlaidFabric/

And remnants:

http://www.thescottishweaver.com/FabricRemnants/