Firstly a link to the blog of Guy Kawasaki - an ex VC / author / proffesional speaker. One of his best presentations is based on his book called The Art of the Start and is definitely worth watching.

Next up is the great video - The Machine is Us/ing Us which is the thing to point relatives at should they ever ask - "What's Web 2.0 ?".

Finally, there are lots of great presentations to watch at TED. Hans Rosling does a particularly entertaining and educational presentation.

Update: 19 April 07... Just found the video Shift Happens.