A lightweight viewfinder hood for point-and-shoot cameras might be useful to those who carry a P&S but not an SLR. From the manufacturer's web page:

"The new H-DCR hood from Hoodman turns your digital camera's LCD screen into a viewfinder. The rubber hood universally mounts to all digital cameras with LCD screens of 1.5 to 1.8 inches in size. Simply strap the H-DCR hood in place over your LCD screen for optimum outdoor glare free viewing. Each hood utilizes a 2X magnifier to allow close focus on the LCD screen. The H-DCR hood from Hoodman collapses into itself for compact storage. The price is compact too! Just $24.99"

The hood would cover some of the buttons, so I don't know how well it'd work in practice, but it's something to keep in mind.