Orbital Viewer, written by David Manthey, is a fantastic program for displaying electronic orbitals. The program has many different orbital-viewing options that are somewhat cumbersome to learn how to use. However, it is easy enough to learn how to use the program at a basic level. It is a great resource for teaching students about orbital shapes and the rules, nomenclature and notation of the quantum numbers n, l and m. Below are screen shots I have captured of 2s, 3p and 3d orbitals while using the program:
A 2s orbital A 3 p orbital A 3d orbital
This program provides a great way for students to visualize the very abstract concept of the electronic orbital. I have found it extremely helpful when teaching concepts such as quantum number notation, electronic shells, electronic subshells, nodes in orbitals, the various quantum number rules (the quantum number, l, must be an integer between 0 and n - 1, for example), and many other ideas related to electronic orbitals. You can download a copy of a worksheet here that I have written that guides students through using the Orbital Viewer program to explore many of these concepts.