You can do just fine indoors if you use indirect lighting and bounce flash like Chuck mentioned.
The difficult part of flash photography is that you normally can't see the result of the flash prior to the exposure. You can overcome this by taping a small flashlight like a mini mag on the flash. This will give the same reflections and shadows as the flash.
If you have a solid tripod the light source doesn't need to be extremely bright since the subject isn't going to have any movement. This will allow you to get by with indirect room lighting and reflectors to produce shadow and glare free images.
