Hi Milky. Just seen this. You can pay a fortune and use pocket wizards as you say to fire flashes off camera. One trigger mounted on the camera and a receiver for each flash you want to use. At the moment no TTL possible though such a versio is coming out. Very expensive and much cheaper alternatives available if starting out. Check out Yongnous which a lot of my contacts use and fire reliably - RF602s I think. Trigger and 4 receivers for about £70. Can use them with any flashes then - cheap as you like.
Don`t know what you shoot with but hte Nikon Creative Lighting System (CLS) is also available to many Nikon users. I used it with my D80 and now with my D700. With this you can trigger off camera suitable Nikon flashes (SB900,SB800 and SB600`s ) with your on board flash. You can have the onboard flash contributing or not to the overall shot on adjusting settings in camera and you can shoot manually or let the camera and flashes work it out TTL which works great. You can mount an SB800 or 900 and use this as the onboard master. This gains you an extra group of flashes. With the onboard camera you can only have two groups of flashes working ( enabling you to have power higher on pne for key light or lower for hair light etc).
I persoanlly have mainly used CLS so far. This has worked for me in every location bar one Always works indoors as the infra red signal bounces off walls etc to targe sensors int he flash. Outside it has usually worked too. You will read that you need line of sight to flash sensors - not always true as signal can bounce off other structures but worth trying to get that to make sure. The CLS trigger method does not work over the distances of the radio controllerd triggers like PWs and Yongnous but is there in your camera already and offers a starting point - if you can afford the Nikon flashes. I got 2 of mine cheap second hand or would have gone the Yopngnou route and might still do now I have changed my camera for the extra distancs if I find I do that many shoots outside.
This link might help you:
http://support.nikontech.com/app/ans...ng-system-(cls)
But go a google for Nikon CLS to get more info. Hope this helps