Don't have the rebel, but I tried both b&w and sepia in my Oly C5050; both looked flat to me. I now do a b&w conversion using the hue saturation layer technique and will then use color variations to get to the sepia tone.
I prefer the tonality of the prints this way rather than in camera.

Thanks Ron, I am trying to figure out how I am going to accomplish the effect for a client that I just started working for whos interested in adding the old timey portraiture to their biz.

The are a couple of different ways to add sepia toning in post processing. In Photoshop CS2, go to Image Adjustment>Photo Filter>Sepia. It's a single-tone filter, but the level is adjustable. Of course, for this filter you need first to convert your color image to BW.

Or, There is software available called ConvertToBWPro2, at www.theimagingfactory.com. With this software, you can both perform the BW conversion and add the sepia toning. Here, the toning is a little more sophisticated, with adjustments for both hue and saturation. It takes some practice to get it right. You can download a 30-day free trial version from their website.

All my suggestions assume that you're using Photoshop - my apologies if you're not.....

Yeah, I was just about to suggest that.

If you can't afford Photoshop (or you just don't want to buy it) you can use GIMP which is a free opensource photo editing program that (IMHO) is just as good or at least good enough.

http://www.gimp.org/