Listen to any speech closely and you'll hear the speech-giver use quotations, often from very famous -and very dead- people. Likewise, you'll hear a lot of statistics, especially from political speech-givers. You've heard that 'a picture is worth a thousand words'? Well, a few statistics, judiciously used, can greatly expand the scope of your speech and bring the topic closer to your audience. HOWEVER, you need to make sure your statistics are as UP-TO-DATE as possible. For example, if you find a great article, from even 3-4 years ago, that has an important statistic in it, don't just use that statistic. See if you can find a more up-to-date number. If you can't, be sure to state, in your speech, the date of the statistic!
Most US statistics originate in a US Government Department or Agency. Here are some of the best places to look. Some actually let you design your own set of statistics, too!
Use these sorts of quotations sparingly. This is different than quoting from an article, book, etc. In a speech, you would usually say: As {famous person} once said [optional: when, or where or under what circumstance]: [the quote]. You might use it at the beginning of your speech as an attention-getter. In which case, you might begin by making the quote and THEN stating who said it, and when. Be careful to verify the quotation's owner. There are many urban legends concerning who said what and what they said. One of the most famous is "Go West, Young Man". Almost all quotation sources say that this was Horace Greeley, when, if you track down the actual quote and circumstances, you discover that actually Horace Greeley was quoting a TERRE HAUTE journalist in a speech! Reader's Digest's June 2009 issue has an article: "They Never Said That!" See also: WikiQuotes' List of MisQuotations.