There are bunch of companies making excellent flash bracket systems. Check out Really Right Stuff and Wimberley amongst others. However, they don't always have exactly what you think you need. The following are a few customized setups that I use.
Twin flash macro setup
There are many ways of setting up with a flash for macro work. One way is is with one or two full size Speedlights inside MicroApollo diffusers. However, that can be a bit clumsy and heavy when shooting on the fly. I wanted a set up with two small flash units bracketing the subject and allowing me to quickly and easily adjust the powers independently. Alas Nikon haven't yet seen fit to copy the Canon Macro Twin Lite MT-24EX which would seem ideal. There are a few other offerings out there (Novoflex make something suitable called a Duo-Flash) but they are expensive.
Nikon have also failed (so far) to come out with a small iTTL flash so I decided to use two SB-30 units and shoot in manual exposure mode. Macro flash exposure is often best set manually anyway so small loss there. The SB-30 Speedlight lets you easily set the manual power and is ideally sized for thi smacro application. The two SB-30 units are coupled/sync'd with an AS-E900 cord. This cord was designed (I think) by Nikon for adding a Speedlight to their Coolpix cameras but is great for applications like this - it incorporates a hot shoe, 1/4-20 tripod screw socket and a 10" long connecting cord to the adjacent flash. You can pick them up on eBay for under $20.
Five flash high speed macro
This is part of on ongoing project I'm working on for high speed macro photography. The setup is basically five Nikon Speedlights (2x SB-800 and 3x SB-26). The flashes are linked by AS-E900 cords and are in "TTL" mode. "Quotes" because I'm actually controlling the flash duration with the TTL fire and quench signals through a circuit I designed myself. The heads can be "closed" in for 1:1 close ups or "opened" for 1:2 or more distant shots.
Unfortunately five strobes doesn't give you five times the GN. It can be calculated if you want using the square root of the number of flashes. So for my 5 flash setup I've got a GN of around 264 (ISO100/ft). More importantly that means that I can expose a 1:1 image at around f11 to f16 for about 1/45,000" at 200asa
I'll post more about this project later. Meanwhile this is what the beast looks like: