America is still using Imperial Measurements in their recipes. There are 6.4 billion Metric users vs. only .3 billion Americans. So this is a four step, when you use your Metric Cups/Spoons, process to convert your American recipes to Metric.
When I first made my first Metric instructable there was virtually no one selling Metric Cups and Spoons. As of 8/7/2010 I have found now only three websites selling to Americans, True Metric Cups and Spoons, and you should spend no more then $5. Replacing your American cups, 237 mL for a Metric cup, 250 mL, and Replace your American tablespoon set, 14.79 mL with true Metric tablespoon set, 15 mL.
Next you need to do, is substitute every American pound (453.59 g) with 500 g. That was easy, no? You will need to convert centimeters, and Celsius. In the end you will actually end up making about 10% more. Why? Because the Metric Kitchen units are bigger then the American units.
Metric is easy -- one gram of water = one milliliter of water = one cubic centimeter.
Water --- 1 g = 1 mL = 1 cm³
1 kg = 1 L = 1 dm³
1 Mg = 1 kL = 1 m³
Find Metric Cups
Find Metric Spoons