The XSi has a few notable features missing from the Canon XS, namely, spot metering. Other useful features include; highlight tone priority, wireless remote compatibility, twice the fps in RAW, 9 vs 7 point AF, 14bit v 12 bit RAW, and a bigger screen. For some, this is worth an extra $100 or so, but it would be better to use that money on a good lens.

Dollar for dollar, the best lens available in the Canon line. This lens is not an all-in-one, but it will give you a good idea of what you want in your next lens purchase. This is a prime lens, so you'll have to zoom with your feet.

Basic hood attachment gives extra protection for your lens. You may or may not find a need for this.

A very nice macro lens with 1:1 ratio.

A little beyond 'budget' reach, but well worth the investment.

Each page of the book has a different technique. Highly recommended.

Useful when editing photos in Photoshop.

Battery back-up if you find you're always running low.

If you use flash a lot, this will be a good accessory to have on hand.

Nice accessory to reduce camera shake, etc. Get the wireless one if you have the XSi.

Optional grip if you find the XS a little awkward to hold and don't want to use the neck strap.

This is a good tool to have for white balance and exposure.

Show off your hard work.