I have 2 different types of monitor stands at my work desk...
One of them is made by Tyke Supply. It's a dual, stacked mount, but they do make triple side-by-side mounts. The reason I mention them is because they are very reasonably priced and very well made.
The only problem I see with this one is that it looks like the three monitors will be flat across. They do have another triple with arms that allow angling them, but it says it's only for 21" monitors or smaller.
If you want to spend more (say around $200-$300), then I would recommend you look at Ergotron's lineup.
They have a couple of different triple mounts. I recommend them because although more expensive, they are very well made and look good.
I actually use 4 of these:
They hold my 3xU2311H and a 2209WA. These things are awesome...! I can move them around just about anywhere over my desk. You set the tension once and then you can move them with a finger.
Here's a pic of my desk at work:
...yes, I know my workspace is cluttered...but I have everything where I can find it...
The U2311H's run off my sig rig, the 2209 off my laptop, and the dual stand holds 1709's that I use for whatever I happen to be fixing (or trying to
I think with either brand, you would be happy. Just have to find a configuration you like.
Just my 2c worth...hope it helps,