These modules were created by Mitsunobu Sonobe, and so we call them Sonobes.These units first appeared in the book Origami for the Connoisseur, by Kunihiko Kasahara and Toshie Takahama.
There are many ways to put them together, which you can find on the web at http://members.shaw.ca/gtarigan/sonobe/index.html
One of them, using only three units, was created by Toshie Takahama, and so we call this assembly Toshie's Jewels in her honor. Another way to assemble the Sonobes was created by Stephan T. Lavavej, instructions for which you may find on his website, http://nuwen.net/poly.html
, since they are much clearer with his photographs.
There are also a bunch of ways you can make the modules which add interest to the final product. Some of these may be found on Meenakshi Mukerji's website at http://www.geocities.com/mmukhopadhyay/creation/sonobe.html
The last time I looked, only two of the links worked, but there are some good pictures. Another interesting site is http://www.fortunecity.com/meltingpot/alabama/179/sonobe_unit.html
, which focuses on cubes.
Finally, if you want some more pictures of how to assemble the modules and a handy table of some of the things you can make with them, try http://home.comcast.net/~meenaks/diagrams/sonoassm.pdf
for another diagram by Meenakshi Mukerji.