While I have found myself using Word to Go for some quick note taking Ashley pointed out Idea Catch to me. This free app by Mad Corgi Software is intended to easily jot down an idea before it is flushed out of your head. You can then use the app to add notes to your idea and store them for later reference.
I have been doing something like this with Memos on my BlackBerry for awhile but I have been trying out Idea Catch today with good results. You can pick up the free Idea Touch app in App World here.
Developer Note: Tap on the cursor to bring up the keyboard in the Description and Note edit fields. An update will be released soon to improve the keyboard behavior.