TypeLink is "a cloud-based personal wiki notepad" for the iPhone, iPod and iPad. "You Type, and it Links! It allows you to organize your information easily and get to it wherever you are."
Its cloud is here. It's also supposed to accessible through the desktop.
I am not going to shell out the money! TrunkNotes, which uses Markdown and can sync through DropBox, seems a better deal. It costs $3.99 (one time).