Radial symmetry

I’d like to model something with radial symmetry.

How do I do this?
I tried the spin tool, but that just extrudes in a circle, it doesn’t make duplicates of mesh.

I don’t know for a true radial symmetry, but for the spin tool, it can be used for duplication
By example :

I have this model, i want to spin it to have a few of them in a circular deployment
http://i.imgur.com/w0uO2.jpg

The “center” of the spin tool is the 3D Cursor, so i move the 3D Cursor in what i want to be the center of my circular effect, but before anything else, i need to view from the top as the spin is dependant too on the angle of view
http://i.imgur.com/uDPpR.jpg

I now select fully the model and press the Spin button, by default the result is :
http://i.imgur.com/HMCYz.jpg

Obviously not what i want, so i edit the settings of the Spin function that appeared in the Operator panel (bottom of the panel to the left of the 3D View) or press F6 to set them up.
The default settings that got the previous results :
http://i.imgur.com/PBBv6.jpg

As i want the circular effect to be 360 degree, i then change “degrees” from 90 to 360 , the result is automatically :
http://i.imgur.com/vdejB.jpg

If i want less of them, i change the default step to a lower setting.
In the end, select all and W -> Remove Doubles as the original model has another one on top of it (due to the 360 degree generation)

Perfect, thank you very much!

If you want to keep the effect live you can use the Array modifier. You have to make an Empty or other object to tie to the modifier.
Then rotate the empty by the degree desired and up the count to match how many times that angle fits in 360.
Then you can mess with it on the fly and apply it at the end.

Aha! I thought there might be a way to do it with arrays, but I didn’t know exactly how they work.

So … what does the empty do exactly? Why are we looking at another object instead of just inputting an offset rotation into the modifier panel?

I didn’t really get why either, and it kept me from really using this until just last night. but it’s really simple and makes it really easy to animate some wild array changes. It seems like one of those power user features that wanting a simple knob.

Because the empty doesn’t only define the amount/angle of rotation, also the point to rotate around. If you move the empty around you can see how.

Oooh! That is really cool and very useful!
Thanks everyone.