Contributed by anonymous.
You can create skinned objects in Blender by creating a set of surface curves, joining them together and then applying a 'skin' over them.
Each curve that you intend to skin must have EXACTLY the same number of points (an easy way to do this is to make a set of duplicates of one single curve).
Be very aware about it if you do real complex models. If it still doesn't work, it's certainly because you have chosen the wrong curve type. Be sure to use Surface Curves for skinning.
Here is a good tutorial about skinning:
https://helium.homeip.net/xoom/tutorials/Cave/Cave.html
Contributed by Matt Hilliard.
So long as your circle/plane/square/ellipse is NOT a mesh object, but is a curve object, this is a very easy task to perform. The term for this technique is called bevelling.
Note: Curve vertices in blender can have sharp points, so a square or other polyhedron IS possible. To accomplish this select the point(s) you want to be corners and hit the V-key.
The steps to accomplishing a bevel are as follows:
1. Create the shape you want to bevel with a NURBS or bezier curve. If you want the curve to close remember to hit the C-key in edit mode. For testing purposes, just adding a bezier circle will suffice. Take note of this Object's name (the heading 'Ob' under edit buttons [f9] )
2. Create and select the path you want your shape to "travel along." This again is a curve and can be open or closed.
3. Find the button BevOb at the bottom of the edit buttons window and enter the name of your shape.
THAT'S IT.
Have fun bevelling.
Contributed by B@rt.
To convert a Text object to a curve or a curve to a mesh, select the object and press ALT+C.