A very good site to get good and to-the-point information without having to click on a hundred buttons first is Wikipedia. Here's on the Champions League:

http://en.wikipedia.org/wiki/UEFA_Champions_League

Have a look at the bottom for the list of past winners. Not that you'll need to be a complete anorak, but you'll need to know some basic facts about who's who. From it, click on anything in blue to know more.

UEFA's own site is the official word
http://www.uefa.com/

FIFA and UEFA are very active in banning YouTube footage, but you can find lots of older matches and highlights there. Try this one from the USA 1994 World Cup, one of the best in the history of the tournament:

http://youtube.com/watch?v=dRUhJkZQorI

Enjoy

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