Many building materials like drywall, lumber, plywood, even siding make wonderful food for mold when wet. Bleach is the first solution that usually springs to mind when dealing with a mold problem.

From Green Living Online, a suggestion for how to deal with mold in a more health and eco-friendly way:

Stay away from bleach
Our first instinct to bring out the chlorine to disinfect and kill mould. But a study conducted by Professor Jeffrey Morrell, Dept. of Wood Science, Oregon State University found that bleach "doesn’t eliminate the surface micro flora." It doesn’t kill the roots of the mould, only bleaches it so we think it’s been cleaned away, when it hasn't. So not only is it ineffectual, its fumes are harmful to both humans and the environment.

Alternatives
A mixture of 56 grams (two ounces) of borax and one quarter litre (one cup) of white vinegar can be sprayed on the mould. Leave it sit for up to 60 minutes and then wipe the area. The mixture will prevent mould from growing back.

There are also several new products out on the market that are natural mould suppressants. Concrobium is a non-toxic anti-mould product available at The Home Depot that is quite effective.