Is there a way to install Cracked Apps to my Iphone without jailbreaking it?

My Iphone is the new one (Iphone 3gs) and it runs on AT&T. My current software for my iphone is 3.1.3. When I say "cracked apps", i mean apps that are in .ipa format. Is there any way without jailbreaking my iphone, that I could install apps that are in .ipa format, so they can sync?