Thanks to NGUYEN DINH Quoc-Huy, we have yet another on-line tool for creation of the lighting and studio-set setups. Below you can try to create your own diagram online, and save a result as *.jpg file on your disk.

Those of you who are lucky to have Photoshop (or need an off-line solution), maybe already know about very handy PSD file by Kevin Kertz.

As you can see above, the PSD file (grab it here: LightingSetup_PSD.zip) has multiple folders with various photo equipment put on separate layers. By switching the layers on and of, by moving the obects around—you can create your diagram offline, in Photoshop.

Sources:
http://www.qhphotography.com/lighting-diagrams
http://www.kevinkertz.com