Canon Digital Camera Rebel
Can anyone recommend the best external flash unit to use with Canon Rebel XTi digital camera?

I'm an amateur photographer who knows little about flash photography and would like to start experimenting. There are lots of Canon EX Speedlite different models to choose from and I'm not sure what is best for me.

Not much you can not do with the onboard flash can be done with an external flash, except with more power. On board flash units are only good when used as a tool to fill flash. Experimenting with light, it requires you to be able to move the light around the object to create back lighting, lighting side key and fill light and lighting of various lamp. To be able to see what you are doing BEFORE you light the subject to take a picture, you need to use some Continuous lighting lamps. You can start with some inexpensive work lamps sold in stores for household supplies such as Home Depot. You can get a couple lamps 500 watts for less than $ 40, then with his camera on a tripod, you can shoot products, adjusting the direction and intensity of light as you learn how control lighting.