The For Dummies website has a page dedicated to measuring ingredients for baking that features a chart of equivalencies. Whereas dry ingredients are often measured by volume, at least in the United States, liquids are frequently measured by mass. In order to use the same measures, some conversion is needed.
RecipeLand.com also has an extensive table of measurements, but it does not specifically give the conversions from dry to wet measures. However, by recognizing that 1 ml. of any liquid with the same specific gravity as water at room temperature weighs 1 g., the metric units can by used as a direct comparison.