I've been a long time user of Dan Rodney's useful and free "Proper Fraction" script for InDesign. Now Dan has released Proper Fraction 2.0, which is available in a free and a "Pro" version. For a measly $75, the Pro version will automatically format all the fractions in a document, use OpenType fraction formatting if available, automatically stroke the numerator and denominator slightly to improve the appearance, allow you to set custom kerning pairs for fractions, and more.
Both the free and the Pro version work in InDesign and InCopy CS2 or CS3.
If you ever create fractions in InDesign or InCopy, you need at least the free version of the script. I'd strongly encourage you to check out the additional functionality of the Pro version.