TED talks are short talks which last 20 mins or less about a range of topics. There are TED talks on all sorts of topics that might interest you.
Here is a short one to get you started, which is one of my personal favourites....
Here is a great playlist of TED talks from kids just like YOU
Adora Svitak
Serina Huang
Memory Banda
William Kamkwamba
Thomas Suarez