For videos you have scirra's official youtube videos which are easy to comment upon while playing and quite easy to translate.
If you want to display the power as in a finished product, check out the best games on the arcade and let the people have a play with those games in their browser.
Be sure to also check the your creations forum.
On the top of my head I think about O-ring, pretty much every chrisbrobs creations and I'm sure there are a lot of other awesome game/WIP sitting in this forum.
Be sure to ask the users their permission first, but I'd think they would have nothing against more promotion.
Look also for the entries of Scirra's competition, as well as the "official" demos.
For a more didactic approach.
A translation/demonstration of the beginner's guide to Construct2 could be a good tool.
You also have this video tutorial that displays quite quickly how to make a shoot 'em up. Also be aware ayzhong is working on it and he should release a new "improved" and updated version of the tutorial in the coming months.
I think that's already a good start.
Also, seeing the number of brazilian members on the website (you can check the introduce yourself topic, there are often new brazilian members there) you should all gather and make a site/forum in your language and build up a community. This will allow you to market C2 more easily and especialy not alone !
Good luck <img src="smileys/smiley1.gif" border="0" align="middle">