I just knitted (not crocheted) a round baby blanket for a friend using Elizabeth Zimmermann's Pi Shawl pattern.
The concept is that you cast on 9 stitches (or whatever, the number does not matter that much) and knit one row, then double the number of stitches by K1, YO. Thereafter, every time you double the number of rows, you double the number of stitches. So a round of K1, YO after the second, fourth, eighth, sixteenth, etc rounds until the blanket is as big as you want it to be. I finished mine off with a ruffle by tripling the number of stitches in one round and then knitting until I ran out of yarn (which was not that much anyway, about 1.5 inches of ruffle). You could finish off with any lace edging or by knitting on a garter stitch strip sideways, but you don't want to just cast off, as it won't stretch as much as the blanket.
It was cute and easy and is pretty adaptable to whatever yarn weight and yardage you have.
I even messed it up and doubled after the twelfth row for some reason, and it came out fine anyway.
If you want the eyelet rounds to be evenly spaced instead of getting further away from eachother, you can always put in an eyelet round by K2tog, yo. This way you have eyelets but not increases.
