I like to buy pillowshams (quilted ones, if possible). I straight stitch them down and use them for bathmats. Really comfortable and washable.
I also like to buy yukatas (cotton Japanese summer kimonos) in the "nightgown/housecoat" section of the thrift stores. I bought a beautiful one this week for $7. It's navy blue with beautiful butterflies. The yukatas are made with 18" wide strips and are super easy to take apart and reuse.
I also bought a gorgeous bronze silk sari with gold embroidery for $13. It's about 20 foot long and 45" wide.
I live near an extremely large, ethnically diverse, city with lots of unusual fabrics which makes thrift shopping amazing.