Tessellation Activities and images (general overview)
http://britton.disted.camosun.bc.ca/jbsymteslk.htm#ACTIVITY15
Interactive Tessellation Creators available on:
National Library of Virtual Manipulatives:
http://nlvm.usu.edu/en/nav/vlibrary.html
(You will need to download a free trial version to use this software)
National Council of Teachers of Mathematics:
http://illuminations.nctm.org/ActivityDetail.aspx?ID=202
Tessellation Animations by artist Makoto Nakamuru