Canon 400D and BG-E3 Battery Grip

Read the Complete BG-E3 review at My Impetus.

The BG-E3 is a welcome addition to the 400d, giving it a
bit more weight and balance (especially with a heavier lens.) In addition, the grip takes two batteries, and makes the 400d much easier to hold. It attaches via the battery door (the door pops off, and the grip plugs in) and then screws on securely via the thumbscrew.
The BG-E3 allows full use of the camera in portrait mode via the buttons on the grip.