If you are at all interested in differences between programming languages and the trade offs a programming language designer must make, and if you haven't already seen it, you really must watch Growing a Language, Guy Steele's Keynote from the 1998 OOPSLA conference.
Not only is the content fascinating, but there's a wonderful twist he starts to reveal at 7:45 (through to 9:00) to do with the whole style of the presentation (which does seem odd, though humorous, at first). It's like something out of Gödel, Escher, Bach where the structure, as much as the surface content, is where the message lies.
I don't want to say too much more, lest I give things away, but the talk really is a masterpiece.
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