Phone
Displays a dialog to dial the number on iPhone, and an error dialog on iPod touch.
Mail
Opens a mail message compose dialog on iPhone, and a new, blank Safari window on iPod touch. "Address Only" fills in only the email To: field. "Address Plus" fills in the To:, CC:, Subject: and Body fields.
Map
Opens the built-in Google Maps client on iPhone, and the Google Maps website (in a new Safari window) on iPod touch. "Query" displays the results of a maps search. "Address" displays the designated address; "Directions" displays the route between two points.
YouTube
Opens the built-in YouTube client and plays the designated video. The two examples represent the two supported YouTube links formats.
iTunes
Opens an iTunes Music Store page within iTunes. "<iTunes store link>" represents "phobos.apple.com/WebObjects/MZStore.woa/wa", which is required to create links to the iTunes Music Store.
The first link takes you to the iTunes Music Store page; the second link opens to an artist's album on the iTunes Music Store.