Penultimate is a pretty cool tool for doing RPG stuff. I made this sample page in just a few minutes, and exported it to my Dropbox so that I could post it here. It also syncs with Evernote if you like that one. The page from the notebook was exported as a PNG file.
The basic idea for an RPG would be to create a notebook of room/campaign notes, maps, etc. You can import regular pictures if you like as well (so you can write and draw around them.
All in all, a pretty cool tool.
edit: forgot to mention that it has different paper styles (including graph paper).
