You must cite your sources in your speech and if required, create a bibliography page to give credit to other folks. I know this sounds stupid but how would you feel if someone stole one of your ideas and made a fortune off of it. I realize you are not going to make a fortune from your speech but it will definitely lend to your credibility if you tell your audience where your information came from.
Make your professor happy and tell where your information came from even if it is from the web!
For examples: check out http://libguides.lamar.edu/APA
Examples of APA Reference Formats http://academics.utep.edu/Default.aspx?tabid=65681