Not anymore there isn't.... We had the key combination that worked on the leaked Froyo DK28 but they removed it in the official build Froyo EB13/EC05.
It was hold your Back Key (capacitive button or key on physical keyboard) and press Home.
But in typical Sammy fashion, they removed it.. LOL.
Plenty of apps on the Market for rooted/non rooted devices to take the place of it.
Rooted I use ScreenShot by GIK Soft.