Here's a set up shot of how I photography my orchids
It's actually really simple, though some of this equipment isn't your every day kind of stuff, but it is fairly cheap and readily available online.
First I have a 100 watt second studio strobe blasting through an old shoe box with a window cut out and some tracing paper taped to the inside. This gives a nice soft, strong light. Then on the opposite side I have a white peice of foamcore to bounce some fill light back into the dark side of the plant.
All flowers look great with some backlight on them so I mounted an older, used, eBay bought Canon 540EZ flash unit with some 1/4 CTO gell over the flash head to color the light slightly orange to help out the color of the leaves. This flash is set to 1/32nd or 1/64th power. It also adds a little fill light. It was triggered using an opticle slave mounted to the hotshoe of the flash.
I like to set the plant on a piece of white construction paper. It bounces a little light back up into the plant. It is also long enough to wrap upward and can act as an infinity syce. In this case I used a piece of black on one side, white on the other foamcore to act as the background.
Here's the set up shot.
And here's the result of the setup.
These were all shot with my Canon 40D. The orchid only shots were done with my Canon 70-200 f4 L lens and the set up shot was done using my Tamron 10-24mm lens.
Did you notice the table cloth in the set up shot? Yes, orchids...