Incase, makers of quality cases since forever, just launched a perforated set of slider cases for iPhone 4. Ultra-lightweight and protective, available in both black and white.
“We’ve combined the 360 degree edge protection of the Slider Case with perforations to reduce weight and volume for a case that gives you the best of both designs. The unique Perforated Slider construction also eliminates rails and bumpers allowing your iPhone to float on an air cushion that protects the phone’s back from impacts and drops.”
Goincase.com: Perforated Slider Case ( $34.95)