The first link (Sew4Home) has a bonus since it re-uses cardboard as a base. Double re-use there if you already have the fabric on hand anyway.
Pink Penguin (ayumills) has a bonus in that the tutorial uses small scraps, quilt-like.
InANutshell is especially cute in that the boxes nest. 🙂
Jezze‘s pattern is extremely tailored looking! Its nice bonus is the lack of interfacing.
UrbanNestBlog is also very professional looking, and although it’s the only tutorial that calls out specifically to using cereal boxes, you can totally use the boxes in any of the other patterns as stiffener.
The pattern from Craftster.org is great with tons of pictures and has sweet handles!!