Listmania!
Must have goodies for the Canon EOS Rebel
By an Amazon.com customer
Canon EOS 6.3MP Digital Rebel Camera (Body Only)Canon EOS 6.3MP Digital Rebel Camera (Body Only)
Buy used from: $249.00
Great camera, get the 20D if you need more buffer or 1600iso, XT is also out now may be a few more features
Canon EOS 20D 8.2MP Digital SLR Camera (Body Only)Canon EOS 20D 8.2MP Digital SLR Camera (Body Only)
Buy used from: $420.00
If you've got the extra $$$$ buy this over a Rebel and a lens, you won't be sorry. Many more features, bigger buffers, noise reduction in high ISO's worth twice as much as the Rebel any day
Canon BG-E3 Battery Grip for EOS Digital Rebel XT CameraCanon BG-E3 Battery Grip for EOS Digital Rebel XT Camera
Buy new: $138.92
This really helps make the camera easier to hold with heavy lenses, if you use IS lenses you need the extra battery onboard for extended shooting
Canon EF 28-135mm f/3.5-5.6 IS USM Standard Zoom Lens for Canon SLR CamerasCanon EF 28-135mm f/3.5-5.6 IS USM Standard Zoom Lens for Canon SLR Cameras
Buy new: $455.60 / Used from: $379.99
If you can only afford one single lens, get this one!
Canon EF 50mm f/1.8 II Camera LensCanon EF 50mm f/1.8 II Camera Lens
Buy new: Too low to display / Used from: $85.00
If you can't afford the f1.4 with USM motor ($300.00) then this is a decent choice for shooting in low light situations where you aren't too far from the subject
Canon Speedlite 580EX Flash for Canon Pro1, Pro 90, G Series, and EOS SLR Digital CamerasCanon Speedlite 580EX Flash for Canon Pro1, Pro 90, G Series, and EOS SLR Digital Cameras
Offers a little more speed than the 550EX and a few extra features
Canon CPE3 Compact Battery Pack for Speedlite 420EZ/540EZ/550EX/580EXCanon CPE3 Compact Battery Pack for Speedlite 420EZ/540EZ/550EX/580EX
Buy new: $155.00
More and faster flashes with several canon speedlights, if you can't afford a professional pack like the Quantum or Metz products this is enough for most of us
Lenmar 2000 mAh NiMH Rechargeable AA Batteries (24 Pack)Lenmar 2000 mAh NiMH Rechargeable AA Batteries (24 Pack)
The 580 needs 4 AA to run the lcd and electronics, the battery pack takes 8 at a time, this will give you an extra set for the cpe3. You'll need them
Digipower BP-CN511 Replacement Li-Ion Battery for Canon BP-511Digipower BP-CN511 Replacement Li-Ion Battery for Canon BP-511
Buy new: $22.77
You want at least 4 batteries if you use the battery grip, never go out without a fully charged set of spares! Can be found cheaper on ebay.
Tamrac 5612 Pro 12 Camera Bag (Black) Tamrac 5612 Pro 12 Camera Bag (Black) 
Buy new: $110.00
Nice big bag to hold all your stuff. Can be found a tad cheaper on ebay.