From your linked definition of iridescence:
Iridescence [is] the property of certain surfaces that appear to change color as the angle of view or the angle of illumination changes.
Thus, the following node setup should suffice:
If you're not familiar with node groups, this will create a new "node" called Iridescence that takes a base color parameter (you probably want white) and a factor parameter (which determines how strong the iridescence is; you probably want about 0.4) to output a color that you can put into a shader. You can see examples of how this works before.
The setup simply takes the dot product of the view vector and the surface normal and maps it to a spectrum. If you're not familiar with vector math, you can basically think of a dot product as a measure of how parallel two vectors are: the dot product of two perpendicular vectors is 0, while the dot product of two normalized parallel (or anti-parallel) vectors is 1.
You can put this node group in any shader and get a nice result. I tried it in a Diffuse BSDF, but putting it in a Glass BSDF might yield some nice bubble renders.
Here's an image of Suzanne wearing her iridescent cloak (the factor is set to 1.0 to exaggerate the effect):
Here's the factor turned down to 40% (lower works in better lighting setups, but my sky texture is blowing it out):
True iridescence is difficult to achieve using Cycles. However, there are ways you can fake the effects of iridescence by shifting the color slightly based on the object normals. This has the advantage of being highly customizable for your particular purpose and much faster than true iridescence would be.
Update: I was able to find an implementation of this using Cycles on this BA thread.
Here is the node setup:
And an example render using the above node setup with different values:
EDIT: Found a better implementation done directly in Cycles. The old BI node setup can be found here.
This is where OpenShadingLanguage can step in. Using an OSL script you can get an iridescence effect.
Michel J. Anders has already done the hard work on his Small Blender Things blog with his surface iridescence shader. You may find some of his other scripts interesting as well.