Prada in the first two photos (Resort '09), then Marni (Spring '09), and Oscar de la Renta (Resort '09).
I'm all for easy ways to snazz up your outfit. For example, take one simple white tee, add one pair of jeans (skinny or slouchy look coolest), and embellish with one bib necklace. If you need help, take a cue from any of the designers here. They've all created their own amazing versions. It's adding a giant dose of sparkle to an otherwise lackluster outfit!
Lanvin (Resort '09), Andrew Gn (Spring '09), Chanel (Spring '09, and btw, what's up with the pseudo-control-top pantyhose?), Iceberg (Spring '09). All pictures via Style.com.