If the software your camera came with doesn't support it, Canon might make something like Nikon's Camera Control Pro, but I'm not familiar with Canon. I shoot with a Sony A700, and it came with tethering software. I used it for grad portrait shooting at my school and they liked it so much that they decided to start tethering.
IMHO, Canon makes everything too difficult with Rebels, so finding tethering software that works might be kind of tough. Good luck though!