Recs.
Updated
This is a budget flash targeted at advanced beginners. It gives you a lot of control over the picture in terms of depth of field, level of illumination, and zoom.
SpecsUpdate
Pros
Pro Can be used in sync with compatible flashes
YN560 can be used to activate other camera flashes from up to 27 feet away thanks to the built-in wireless transmitter. It can also be used in slave mode, activated by another flash or a wireless trigger. You can create groups of connected flashes with models YN560-IV and YN560-TX and use wireless triggers: RF-603 (I/II), and RF-602.
Pro Can be fired frequently
YN560 is faster at reaching its full power after being triggered than an average flash. It's recycle time is three seconds, while many brand flashes (Canon, Nikon) take as long as six. It's even faster if you connect your flash to an external battery pack via the HV port.