I use Canon and have found that it is easiest to just use a couple off-camera shoe cords (Canon OC-E3 or generic equivelant) with a Canon flash. I do MOST of my flash shooting using ETTL and dialing in exposure compensation, when needed. I use a Canon 580EXii flash with a Canon 50D.
I also have additional flashes and have tried using Canon's wireless capabilities. The Canon wireless uses infrared instead of radio, so it doesn't work great outside in bright sun. The ETTL wireless systems that use radio, such as Pocket Wizards or Radio Poppers, are fairly expensive.