Hi,
I just finished an effect which calculate the polygon surface and print it on the polygon.
Where can I share this work??

Could not find...
Thanks,
Cheers,
Patrick

If you haven't shared with the developers, you could do so via the mailing list, and/or through Launchpad, please find links in this topic:
viewtopic.php?f=5&t=646

If you just want to share with the forum, this is one place you might share, but the best place is probably Inkscape Resources (viewforum.php?f=11).

If you think this extension is something that could usefully be included in a future release of Inkscape, then posting it to Launchpad is probably the simplest thing to do. Just open a bug report saying that you've made this extension and that you would like it included in Inkscape, then post the files as attachments. (Opening a bug report for something that isn't a bug may seem a bit odd, but this is the way to make feature requests for Inkscape now.)

see related Bug #269002 in Inkscape: “An LPE to measure area (square) of a closed path” has also an area extension attached (comment #8) - maybe you can merge your efforts?