I've used this effect for some of my layouts and I think it's so cool.

1 Download the sinedots filter.
2 Unzip it into the following folder: C:\Program Files\Adobe\Photoshop 7.0\Plug-Ins.
3 Create a new image, any size. mine is 350 x 350. You don't need to fill in a background color. You can if you want to be able to see your shape better though ^^ So i'll just do black on another layer. 4 Go to Filter, Dragonfly, Sinedots. [I'm teaching you how to use sinedots, i'll have another one on II soon]. 5 You can just play around with the knobs and stuff. but if you want a shape like mine, look:

[Click to enlarge!]
6 Now you can colorize it, add an image, blend it into a layout. Anything ^^ Be original and come up with your own shapes too =D