In case you want to know the UIActivityType strings that Apple uses for iOS development, then here they are:
- com.apple.UIKit.activity.PostToFacebook
- com.apple.UIKit.activity.PostToTwitter
- com.apple.UIKit.activity.PostToWeibo
- com.apple.UIKit.activity.Message
- com.apple.UIKit.activity.Mail
- com.apple.UIKit.activity.Print
- com.apple.UIKit.activity.CopyToPasteboard
- com.apple.UIKit.activity.AssignToContact
- com.apple.UIKit.activity.SaveToCameraRoll

these are useful e.g. when you are using Prime31 Social Networking plugin and you have to use excludedActivityTypes with shareItems.

In case you want to print them via Xcode:
NSLog ( @"facebook: %@", UIActivityTypePostToFacebook );
NSLog ( @"twitter: %@", UIActivityTypePostToTwitter );
NSLog ( @"weibo: %@", UIActivityTypePostToWeibo );
NSLog ( @"message: %@", UIActivityTypeMessage );
NSLog ( @"mail: %@", UIActivityTypeMail );
NSLog ( @"print: %@", UIActivityTypePrint );
NSLog ( @"pasteboard: %@", UIActivityTypeCopyToPasteboard );
NSLog ( @"contact: %@", UIActivityTypeAssignToContact );
NSLog ( @"camera roll: %@", UIActivityTypeSaveToCameraRoll );