Does anyone know a good way to prepare peppery radishes?

If you have just the radish bulbs:
http://www.finecooking.com/recipes/butter-braised-radishes.aspx

If you have the bulbs and greens:
http://www.finecooking.com/recipes/honey-roasted-radishes.aspx

If you want to make a spring veggie medley:
http://www.finecooking.com/recipes/spring-vegetables-ragout.aspx

To cut the calories down a tad, reduce how much butter/oil the recipe calls for - I find they go a bit over the top on the fats. But I've made all three of these and they're very tasty.

Use them in a Tom Yam soup.