If you mean from your home screen tap and hold then drag to the bottom. It will turn red and you can let go. It will be removed from your home screen. If you mean from the app drawer the only option is to remove the app through the market. Going into downloads and uninstalling. Or you can go into settings, application, manage applications and find it there and uninstall that way. Other than that I am not sure.
You can't add apps in the drawer as that is where they all are.
You can create a folder on your desktop and put apps in there you do use regularly. I started with a games, tools, gps, etc folders. That helped to keep them organized. I now use Ultimatefave on the original droid. There are other app organizers in the market too.