Don't we all love to make Lighting diagrams? They help us explain our lighting setups. They can also help us design a setup in advance.
UPDATE 3: The The Lighting Diagram Creator now supports export to jpeg. Man, Huy has really done great work with this one, It even allows adding sound gear.
UPDATE2: Lets try and make the online diagram creator complete. read on for making a stamp on the history of online lighting diagrams tools.
UPDATE1: Due to licensing issues the tool has been revised to use Don Gianatti PSD file - It is still a great way to create lighting diagrams online.
In the past I have written about a great PSD file created by Kevin Kertz. This PSD file allows you to describe (almost) any lighting setup you create. I have used this excellent method myself in Shooting The Team series.
There are other lighting diagrams creating tools out there, but none was as complete as Kevin's. The only drawback to the PSD file is that you had to install Photoshop or The GIMP to use the file (yap, PSD is Adobe's Photoshop native format).