A lot of people are unaware of the possibilities of the ExtrudeOp operator.  See below…

Fiddling with the ExtrudeOp options

Try this yourself:

1. Get a sphere. (My screenshot example was a half-sphere.)
2. Select all polys. (Press Y to enter poly mode then Ctrl+A to select all.)
3. Press Ctrl+D to Extrude.
4. In an Explorer open your object’s operator stack, find the ExtrudeOp and open its PPG.
5. Turn off Merge, then fiddle with Length, Inset Amount and Subdivs.
6. Then in the Transform tab, play with the sliders there.
   You can get some very interesting (and often abstract) results! 😉

*UPDATE [21/05/10]*: A buddy of mine who uses Maya informs me that the mayan Extrude has options to do this as well if you peek in the channel box. Just so you know. 😉