The 3rd Party iPhone applications are starting to roll in. Here's TUAW's list of currently available packages. I'll update this list as more apps become available and we hear back from more developers.
Hello World. Hello World Demo
KBDemo. Proof of concept Keyboard demo. Part of the larger Mobile Terminal for iPhone project.
Do Shell. Runs shell script embedded in App. Can be customized by end user.
TextViewDemo. Allen aka Pin's excellent UITextView sample.