You can have look around your surroundings. You will find many famous quotes on greeting cards, calendars and diaries. Whenever you find a memorable quote, just cut it and paste int into a scrapbook so that it does not get loose in shuffle of papers.
Whenever you read, keep a journal next to you so that you can easily note down the nice points that touches you and express your feelings when you read something. There are many great quotes that you can find online. When you are using a quote in blog post, it is considered as good to link back to where you find the quote. You can also use the bookmark system or tagging so that you have track of your favorable ones.
Read the autobiographies of your favorite people. When they express their story in their own words they often give out quotes. This way you can have unique collection of quotes that could surprise people when they hear these. Listen carefully to the celebrity interviews. Many times they express their feelings in quotes and its obvious that the quotes express by famous celebrities become famous quotes
While searching for famous quotes to use in your presentation or speech, all that is required to visit Google and there you could find nice quotes for any possible presentation or speech you could ever imagine. You could also choose to go to library and find any book of famous quotations or any good book or quotes. There are plenty of good books. Most of them are categorized by keywords like optimism, success and inspiration etc. Find the quote that relates best to your presentation or speech and use it in the beginning of your speech and possibly to close it.