TextExpander touch [$1.99 on sale, $4.99 after Sept. 9 - iTunes link], is the iPhone (and iPod touch) version of Mac favorite TextExpander, an app that takes short bursts of text and expands them (get the name?) into longer passages.
TUAW has the details, especially on how the lack of background multitasking for 3rd party apps means the iPhone versions works (and works around) a limitation it doesn't face on the desktop.
Check it out and let us know what you think. Or let TextExpander embiggen your thoughts. What'evs.