Nicole Richie and Joel Madden are about to make it official. The couple will tie the knot after three years of dating, she announced so during tonight's taping of  "The Late Show With David Letterman." Also,  just last week Nicole was spotted browsing at bridal gown designer, Monique Lhuillier's, LA shop with Joel's twin brother Benji. It's about time, those two are so cute together!