I've made two extensions that I want to share with the community .

1. Close curves - I is really simple extension that close all open curves in the selection. I've made it when I needed to use curves made in Incscape in OpenOffice. OpenOffice wont fill curve if it is not a closed curve, even if starting and ending points have same coordinates. (All text being converted by Path->Object to path becomes open curve. See example.)
What extension really do: it simple adds "Z" at the end of "d" parameter of the curve and before each "m" or "M" if there's no 'z' already.

Close curves extension is available here: http://www.cnc-club.ru/forum/viewtopic.php?f=15&t=37 .





2. Gcode tools - It is more complex plug-in that exports paths to Gcode special language that is being used in CNC machinery. This plug-in is a kind of remake of Export as GCODE.
Main feature is that new plug-in interpolates paths with biarcs instead of polylines, giving smooth result without rebuilding the path.

Gcode tools extension can be found here:
English support forum: http://www.cnc-club.ru/forum/viewtopic.php?f=15&t=35
Russian support forum: http://www.cnc-club.ru/forum/viewtopic.php?f=15&t=34
Here are two pictures, the first one shows resulting Gcode in EMC2, the second - is little how-to: