Craft Buds, Mary used a shower curtain base to make her blanket waterproof! It also cleverly folds into an attached tote bag, so it's always ready to go.
Erin at Sew, Mama Sew included corner rock pockets on her patchwork blanket. Once filled, they keep the blanket from blowing away. Genius!
Cherry Menlove includes an adorable blanket holder in her tutorial. It buttons around a rolled blanket and has a handle for easy portability. Why didn't I think of that? (Images: As linked above.)