A sturdy and easy to fold modular origami, by Carmen Sprung.
An origami arabesque, by Mio Tsugawa.
A very nice modular origami that has the possibility of being expanded.
Another modular origami, from David Brill.
A modular box with its lid, by Tomoko Fuse.
Modular origami by Thomas Hull, five tetrahedra inside each other.