Here's a simple and easy improvement over bounce cards such as Peter Gregg's www.abetterbouncecard.com: a double bounce card. It consists of two foam bounce cards facing each other.
Here are its advantages over a regular bounce card:
1. Can be used in portrait orientation whether the camera is tilted clockwise or counterclockwise.
2. You can use the bounce card sideways on camera left or camera right order to add directionality.
3. Doubles as a snoot.
DOUBLE BOUNCE CARD AS SNOOT:
To give you an idea of how it performs as a snoot, here are comparison shots of a flash at 24mm and at 105mm, with and without the double bounce card as snoot:
Flash at 24mm without snoot:
Flash at 24mm with snoot:
Here are a few sample shots where I used the double bounce card as a snoot (flash was off-camera, triggered via CLS).
I don't have samples where I used the double bounce card as a bounce card because I believe in almost any situation where a bounce card can be used effectively, you can just bounce the flash directly and get better results. (To learn why, please read this introduction to basic lighting)
EFFECT ON FLASH EXPOSURE:
The folded bounce card does cover the front of the flash. Does this affect the flash exposure? It depends. On TTL mode, there is no effect on flash exposure because the flash exposure is measured through the camera lens, which is not covered by the folded bounce card. On auto mode, where the flash exposure is measured by the flash itself, the folded bounce card will interfere with the flash exposure. To learn more about TTL vs. auto mode, pls. read the TTL FAQ.
The folded bounce card may also interfere with the AF illumination (some external flashes project a red light on the subject to help the camera focus especially when it's dark). Finally, the folded bounce card may also interfere with the ability to trigger the flash optically (if you're using it off-camera).