A collection of colorful, simple, square bean bags is always popular with little boys.
Or drawstring bags to stash a collection of small toys to keep in car or diaper bag.
Pillow cases made from novelty fabrics that appeal to them -- the Dr. Seuss fabrics would be super-cute, and a nice tie in if they like the Cat in the Hat show on PBS.
Baby bibs are easy to make, and useful for the youngest baby.
RST