American Rhetoric has compiled a list of the top 100 speeches, and most include links to audio and transcribed versions.
The #1 one speech is Martin Luther King Jr’s I Have a Dream, which deserves its position, but one of my favorites is number 8, Ronald Reagan’s Space Shuttle “Challenger” Tragedy Address.
There are several in the top 25 that I’m not familiar with. Maybe I should have listened more in history class.
(via kottke’s links)