I just purchased the Index Card app for iPad. It’s a notecard system for writing that synchs with Scrivener via the Dropbox service/app.
This tutorial explains it in detail: http://www.youtube.com/watch?v=qoGevEX1SUM
In short, Index Card requires a “flat” structure, so if the Scrivener project contains folders with documents inside, Index Card won’t recognize it. In order to use Index Card, the Scrivener project must be set up with Collections. The documents are selected and added to a Collection (I named mine Index Card Synch). The Collection is saved in the Dropbox folder through Scrivener’s menus (see the tutorial for more detail). Now, the file can be opened on the iPad with Index Card and edited.
Looks really useful at this point, but I’m always a bit hesitant to synch things over a network because of the danger of file corruption. There are several threads on the Literature and Latte site (creators of Scrivener). http://www.literatureandlatte.com/forum/viewforum.php?f=22
This is important to note — how Index Card stores the text from Scrivener (it’s on the “back” of the index cards, something that wasn’t evident to me at first).