Good speeches from all around the world
Good resources for seeing the best of speeches are :
Toastmasters It is an international organisation which runs as clubs at different places and they also have annual public speaking competitions. You can see the videos at their youtube channel.
TED talks : TED Talks are influential videos from expert speakers on education, business, science, tech and creativity. These are short talks (less than 18 minutes), delivered in an effective way. You can see the videos at their youtube channel.
For children speeches, the best resource is Making Champs youtube channel, which is the largest collection of speeches by children for children. You can see the videos at their youtube channel.