This past summer, I spent 2 weeks conducting workshops throughout Austria. At one of those workshops, I demonstrated the creative use of a really cool modifier. I carry a set of barndoors in my lighting kit at all times. I use a set of speedlight modifiers produced by Gadget Brando out of Hong Kong. I wrote a post about these modifiers back in 09.
This is a photograph of Wolfgang at one of those workshops. I used a Lumiquest Softbox LPT for the main light and one SB-800 with a set of barndoors for the background. Barndoors allow you to shape the hard light coming from your speedlight to almost any shape within the square to rectangle shape. Barndoors are very flexible in that they allows you to create more interesting backgrounds and also focus your view attention to specific areas of the photograph.
In my lighting kit I usually carry 2 sets of barndoors. Their light weight and take no space in my bag. I'll also use barndoors on lights that are place facing towards my camera position. I can use the adjustable blades of the doors to help prevent flare in my lens. You can see here in the photo below how that might be used.
I have a Small Strobes, Big Results workshop coming up on the 25th of Feb. here in Denver. If your interested in attending, you can learn more about that HERE. The full website for Small Strobes, Big Results is HERE. DT