I came from a province in Canada where the sun only shines two times a year - and one of those times is in the middle of the night so if you get up late you miss it. It was so gloomy the grizzly bears were fitted with fog lights so they could find the campers in the dark.
Imagine my pleasure to find Western Australian weather. No more troubles with gloomy skies at weddings. All sunshine and bluebirds. Yeah - all sunshine until 1: The clouds sock in, 2: Those bluebirds are nesting magpies, and 3: The bridal couple want to be fashion stars. Not gas giants or dead dwarf stars either...
The bird problem is still with us, because you can't shoot them. So is the bridal couple problem, because you can. We can't solve these, but we can banish the clouds. Come into the shop and have a look at the Lastolite soft boxes.
I use a Nikon D300 with an SB700 flash on the top and a Gary Fong Lightsphere on top of that. It throws fill light in beautifully from the front if there is some form of main light coming from another direction. Here's where the Lastolite Sun On A Stick comes in. I put a Lastolite Ezy-Box softbox on a Nikon SB600 flash and this on the end of a Lastolite extension pole. My assistant, Igor, acts as the lighting man, moving as directed to throw main shots onto the bridal couple if there is no sunlight to illuminate them. He can functionin under eaves, trees, or railway bridges. Also inside dim old churches - the softbox light coming off the top of the pole is not too harsh in these delicate environments.
At this point I must record my wonder at being prohibited flash in one religious venue upon the grounds that it would disturb the sanctity of the affair. I privately reflected that the Proprietor of the church was responsible for the entire solar system and everything out past that and so far kept the Sun shining without too much trouble...but then the mother of the bride had a series of short words with the minister and the objection was withdrawn. Remember that at your next wedding - if you cannot get the Royal Marines, get the mother of the bride.
Back to the light. The Nikon system of IR control for the outboard flash works well inside a building but might be fooled by high light levels outside. If this is a problem, look for one of the Pocket Wizard TTL control box systems - you'll never have triggering troubles. If you are a Canon user, remember that the new Canon 600 flash has an inbuilt radio receiver. However you do it, you get to control how intense the outboard light is from the camera position - as long as you and your light operator understand what you are trying to achieve you can get a real studio effect in the most confused light. This is a great way to cope with the dappled mess you find under trees and in Gazebos.
Small Note: In the dear old film days we tried this with a Radio Slave outfit and Metz 45 flashes and sometimes it worked. But I had to communicate the instructions to Igor across the void by means of hand signals and pre-arranged letters on the Metz flashes - it was all very crude. Now I can dial what I want from down the front and he just moves into position. It is really the secret to success for shots at receptions of speeches and dances, though surprisingly the frontal flash still looks better for the cake cutting.
Final Note: If you are a wedding worker who never intrudes into the sanctity of the ceremony and always stands off to the side with a 70-200 lens and falls into a gasping fit when the idea of flash is suggested....well fall over that way and don't get in my way. I have a flash and sharp elbows and nobody is going to get between me and bride. She is going to be illuminated if it kills her.