Fruit picking is sure the easiest option, that doesn't take work experience, and allows you to work all over Europe, at just about any season ! If you browse through the Study and work abroad forum
, you'll find a few answers. For example these two threads :
Grape picking in France
Car washing in Europe
There are more, I just had a quick look into the forum to give you ideas. Also if you could grab one of the available books listing jobs abroad, you'd have specific addresses to contact. The most known is "Work your way around the world" by Susan Griffith.
Good luck !