ABOUT THE YONGNUO YN-560EX
The YN-560EX (formerly EX600) is a manual flash but can act as a wireless TTL slave via Canon or Nikon's wireless flash commanders (yes it is cross-compatible with Canon and Nikon). I was excited about this model because it's only $109.99, less than the YN-565EX (which has wireless TTL as well as on-camera TTL and costs around $160 for the Nikon version). It is one of the cheapest wireless TTL flashes available. (At the end of this article I will post other wireless TTL alternatives.)
The YN-560EX should not be mistaken with its similarly-named predecessors, the YN-560 (a purely manual flash) and the YN-560II (an updated version of the YN-560, also purely manual). The 560EX was previously known as the EX600 but its name was finalized as the 560EX.