We are not big time flash users, however there are moments when a good flash is essential to getting a great photo. We always struggle with remembering how to set it all up, master slave etc.. but in the end we get there. I think one of the best tools we found was the pocket wizards, they are great and make it so easy to set up the flashes wherever we want. They are definitely worth checking out.
SB-900 AF Speedlight:
I don't really have much to say on flashes other than they are essential at certain times and that this particular flash is a great unit.
It has many improvements over previous flashes and it performs magnificently. It is also one of the biggest flashes I have ever had, sometimes that is a problem when packing everything. Hmm I think I always have a problem packing everything, no matter the size, there is always too much.
Anyway, this in an awesome flash, best Nikon has to offer as of June 2011 - Check out the specs at Nikons Website.
SB-800 AF Speedlight:
This was a good flash when we got it and it still is, however now it is generally used as a slave unit with a pocket wizard attached to trigger it.
For me, flashes are one of those love hate relationships. When everything goes right I love them, but generally I hate getting there.
We have a beautiful owl photo that would not have happened without a dual flash setup.
Check out the Nikon site for more info:
POCKET WIZARD:
These things are just awesome !! Period !
You can have several units, we have three. Each one can be set as a master or slave and there are different channels that can be set.
They fire the flashes remotely every time, they don't have to have direct line of sight to the flash which is great. They have even newer models that are smaller and just as powerful.
Generally one unit attaches to your camera, and you set up one or more slaves to be triggered from that master unit. check out the companies site, just google pocket wizard.