Flash unit on my Nikon

There are many ways to improve flash photography. One solution is to use the bounce card, or to use as you said a bigger, improved bounce card. Another much better solution is to use a wall or corner or ceiling in the room you are in to bounce off. Tilt the flash unit head to the side or up and bounce it off the wall, making sure it hits the subject.
Other options that are much more powerful is to use your flash unit OFF camera. This can be accomplished with an off-camera-shoe-cord, or sync cable if the D80 of yours has one of those ports.
Check out www.strobist.blogspot.com for an amazing resource of off camera lighting.

are you talking about the shadows, of your subjects, on a wall? You’re subjects are either too close to the wall or your flash is too strong. If you are in a tight space, there are ways around this. Bouncing the light (as mentioned above) will work, but you will need it to be in the correct distance from a wall or ceiling. If its too far away or its a dark color, it won’t work. I do not know what flash you have, but you can buy a diffuser or sock that goes over the flash head. This will soften the light and create a more pleasing effect. Flash is a very tricky animal and pratice makes perfect. I can go into more detail, but it’s really trial & error. Every situation is different. Feel free to message me if you any questions.