Flashes How Do I Trigger My Flashes Off The Camera Without Wires. I Have A Small Budget.?

How do i trigger my flashes off the camera without wires. I have a small budget.? - flashes

I have a Nikon D40 and have two additional longer spark build one. I want to be able to use two additional trains for you to start a small study of freinds and family but want to be really able to go wireless flashes for them. I know it's possible, but I do not know the best way to do this.

Any tips?