Is this Illuminations unit (Grades 3-5, but I've adapted it for higher grades and a variety of subjects), one of my old standbys, of interest to you?
Geometric Solids and Their Properties - http://illuminations.nctm.org/LessonDetail.aspx?ID=U122
You don't give the grade level of your students, so here is another Illuminations unit for the younger students (Grades PreK-2) on
Investigating Shapes (Triangles) - http://illuminations.nctm.org/LessonDetail.aspx?ID=U52
Science Netlinks has a lesson (Grades 3-5) called
What's a Shape - http://www.sciencenetlinks.com/lessons.php?DocID=135 that discussion properties of shapes and tangrams, a fun application of shapes and their characteristics.
Here is an interactive, enhanced from the days when I used it, where students can discuss and sort shapes by their properites, at the same time setting their own rules.
Shape Sorter - http://illuminations.nctm.org/ActivityDetail.aspx?ID=34
Here are a few more possibilities:
Cuttting Corners -- a lesson from Illuminations for grades 9-12 provides an excellent opportunity for students to talk about the names and attributes of shapes they do not regularly meet.
Isometric Drawing Tool -- from Illuminations for grades 3-12, this lesson uses an interactive tool to create dynamic drawings on isometric dot paper. Draw figures using edges, faces, or cubes. You can shift, rotate, color, decompose, and view in 2‑D or 3‑D. Start by clicking on the cube along the left side; then, place cubes on the grid where you would like them.
Congruence Theorems -- an Illuminations activity for grades 9-12 to investigate congruence by manipulating the parts (sides and angles) of a triangle. If you can create two different triangles with the same parts, then those parts do not prove congruence.
Dynamic Paper Tool -- this is one of my favorites from Illuminations for grades K-12. This application allows you to create images of nets for 3‑D shapes, tessellations of polygons, number grids with any number of rows, columns, and integers, spinners with various numbers of sectors, and more! You can then create a PDF worksheet with the images you choose, or you can export the images to JPEG format for use in other applications or on the web.
There is a very active math group in the Community Learning Math which you may wish to join to gain more teaching ideas for your classroom.
Verizon Thinkfinity Community Host
I also found this site on national geographic kids