But do you want to send a sms from an application? From an application you can start the SMS application with a url with schema sms (see apple documentation), but you still need to input the text manually.
In strict alphabetic order :-)
AlliDator (for data and lists)
ChessAndBack (for free moments)
Facebook (ah, friends)
Myst (when I feel nostalgic)
WheatherBug (I travel often)