This is the best portrait lens I own. It's expensive, but worth every penny.

This is an essential piece of equipment. Infants will lose attention as soon as you put your face behind the camera. You need to mount your camera on a solid tripod.

Along with the tripod, this is the most important piece of equipment you can buy to get great pictures of your infant. A cable release allows you to take pictures without ever having to disappear behind the camera. Keeping constant visual contact with your infant will keep their attention and allow you to get great smiles.

Forget the on camera flash on the 50D. For artificial light, you need a hotshoe mounted external flash. This unit will do more to increase the quality of your portrait photos than anything else on this list. The most important aspect of this flash is its ability to redirect the flash. It looks particularly great when you bounce it off the ceiling to better mimic natural lighting.

This battery grip accomplishes two vital tasks. First, it holds an extra battery to help prevent you from running out of battery power in the middle of a shoot. Second it balances the Canon 50D much better, making the camera much more comfortable in your hands. Additionally, there is a second shutter release button on the battery grip making pictures in portrait mode much easier to take.

This is a great camera bag. It is well made and well thought out. The bottom portion will carry your camera, all of your lenses and flash. The top portion will carry all of your miscellaneous gear. There are extra pockets for batteries, CF cards, etc. Plus, there is a laptop pocket too. This bag will get all of your gear to wherever you want to go.