Distribute object on circular path?

You'll want to investigate "tile clones" but it's a bit of a mystery to me ...

a) Tiled Clones
If the twelve objects are identical copies, you can use 'Tiled clones' to arrange them as clones in a circular array:
<http://tavmjong.free.fr/INKSCAPE/MANUAL_v16/html/Tiles-Tricks.html>

If these are twelve different objects, it is more difficult to arrange them in a 'semiautomatic' way:

b) Place Objects On Path
There's a user-contributed external extension you could try:
<http://wiki.inkscape.org/wiki/index.php/Extension_repository#Place_Objects_on_Path>

c) Scatter Along Path (enhanced)
Alternatively, the 'Modify Path > Scatter…' extension has seen an enhancement recently:
  Bug #617045 in Inkscape: “Enhancement to the Scatter Extension”
  <https://bugs.launchpad.net/inkscape/+bug/617045>
Download&install the latest enhanced version attached to the bug report if - based in the discussion there - you think it would allow you to "scatter" the objects (put into a group) evenly along a circular path.

If you "only" need to arrange twelve objects in a circular array, you could also consider doing it 'semi-manually':

d) Manual Arrangement
1) stack all objects on top of each other
2) select one after the other and do these steps:
3.1) drag the rotation center to the center of your imaginary circular array (use e.g. guides to mark the center, and snap the dragged rotation center to the guides intersection for more precision)
3.2) rotate the object with the mouse while pressing the 'Ctrl' key: this will restrain the rotation angle to a multiple of the Rotation snap angle (as set in the preferences - default: 15°).
4) repeat step 3 for each of the stacked objects, increasing the rotation angle by 30° each time

See also:
<http://tavmjong.free.fr/INKSCAPE/MANUAL/html/Transforms.html#RotationCenter>

Minor correction:
- Alternatively, the 'Modify Path > Scatter…' extension
+ Alternatively, the 'Generate from Path > Scatter…' extension