This is the one I use...quick and easy:

* Exported from MasterCook *

Sweetened Condensed Milk

Recipe By : Katie
Serving Size : 0 Preparation Time :0:00
Categories :

Amount Measure Ingredient -- Preparation Method
-------- ------------ --------------------------------
1 1/2 cups sugar
2/3 cup evaporated milk
4 tablespoons butter

Heat and stir until butter is melted and sugar is dissolved. Makes about 1 1/2 cups. One can = 1 1/4 cups.

Here's another

3/4 c. granulated Sugar 1/4 c. Margarine
1/3 c. water 1 c. powdered milk

Bring sugar, water, and margarine to boil, stirring to dissolve all the sugar. Remove from heat and pour into blender. Add the 1 c. powdered milk and blend until smooth. Refrigerate any you don't use right away.