If you want to retain ETTL functionality, then you either want the Pocketwizard Flex (and/or Mini) or the Radiopopper PX units. If you can live without ETTL (by adjusting you flash power manually), then there are many cheaper options available other than Pocketwizards. Some include:


RF-602 on ebay


Cybersyncs


Radiopopper JrX


Those are my current recommendations for manual off-camera flash triggering. I used to recommend the CTR-301p units from ebay, however, from what I've read the RF-602s seem to be a more solid and reliable product. Also, I am certain that Cybersyncs and Radiopoppers can trigger your camera's shutter release wirelessly with the right kind of motor cord. If you're just starting out in off-camera flash, I'd suggest you go to the strobist blog and read the section labeled Lighting 101.


If you'd like a little more information, you can ready my posts related to off-camera flash here.


Personally, I use Cybersyncs. In fact, I used a Cybersync receiver to trigger a Vivitar 285 flash for this shot yesterday. The subject's back is to the sun so the flash is creating the main light on the left side of her body. The ambient light is acting as my fill light.