1/4 cup of butter
1 1/4 cup of flour
1/4 teaspoon of vanilla extract
1/2 teaspoon cinnamon
1/2 cup of sugar
1 pinch of salt
Mix the butter with 1/2 cup of water. Stir on low heat until the butter melts and add the salt. Add all the flour and beat with a wooden spoon until it is all the same (about two minutes). Remove from the heat and let cool down.
Add the eggs, one by one, beating the mix after adding each egg. Add the vanilla and continue beating until the mix surface is shiny.
Meanwhile, heat oil in a deep pan (at least one and a half inches deep) to 380F. Serve the mix with an icing bag, using a half inch nozzle. Cut the mix every two inches before it hits the hot oil. Fry until they are golden, and let drain on paper towels.
Roll them in a bowl with the sugar and cinnamon.
Another really good recipe: http://www.xmission.com/~dderhak/recipe/churros.htm