Jelly Roll race or 1600 quilt. One Jelly roll (40 strips) of 2.5" fabric. Cut off half the first strip. Sew all the strips together. Sew the two ends together lengthwise. Snip the other end when you get there. Bring the ends together and sew together lengthwise. Continue until it's the size you want. Makes a lap sized quilt.
If you search Jelly Roll race quilt here you'll find examples of how to calculate the final sizes.
Variations - sew the strips together at a 45 degree angle
Variation 2 - sew an accent square between each jelly roll strip.
Variation 3 - cut your own strips of a different width for a different size quilt, and/or change the number of strips used.